diff --git a/CMakeLists.txt b/CMakeLists.txt
index 2b5a2842c..cf3b62246 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -15,6 +15,9 @@ set(CMAKE_MODULE_PATH ${CMAKE_MODULE_PATH} "${PROJECT_SOURCE_DIR}/cmake")
 # Build options
 #
 
+# Experimental features
+option(EXPERIMENTAL_SHA256     "Enable experimental SHA256 support (for R&D/testing)"  OFF)
+
 # Optional subsystems
 option(BUILD_SHARED_LIBS       "Build Shared Library (OFF for Static)"                  ON)
 option(BUILD_TESTS             "Build Tests using the Clar suite"                       ON)
@@ -107,6 +110,7 @@ include(IdeSplitSources)
 include(FeatureSummary)
 include(EnableWarnings)
 include(DefaultCFlags)
+include(ExperimentalFeatures)
 
 
 #
diff --git a/cmake/ExperimentalFeatures.cmake b/cmake/ExperimentalFeatures.cmake
new file mode 100644
index 000000000..f23bfe376
--- /dev/null
+++ b/cmake/ExperimentalFeatures.cmake
@@ -0,0 +1,12 @@
+if(EXPERIMENTAL_SHA256)
+	add_feature_info("SHA256 API" ON "experimental SHA256 APIs")
+
+	set(EXPERIMENTAL 1)
+	set(GIT_EXPERIMENTAL_SHA256 1)
+else()
+	add_feature_info("SHA256 API" OFF "experimental SHA256 APIs")
+endif()
+
+if(EXPERIMENTAL)
+	set(LIBGIT2_FILENAME "${LIBGIT2_FILENAME}-experimental")
+endif()
diff --git a/include/git2.h b/include/git2.h
index 2961cc3e5..3457e5f04 100644
--- a/include/git2.h
+++ b/include/git2.h
@@ -28,6 +28,7 @@
 #include "git2/diff.h"
 #include "git2/email.h"
 #include "git2/errors.h"
+#include "git2/experimental.h"
 #include "git2/filter.h"
 #include "git2/global.h"
 #include "git2/graph.h"
diff --git a/include/git2/deprecated.h b/include/git2/deprecated.h
index c32abeeb7..52864ebe1 100644
--- a/include/git2/deprecated.h
+++ b/include/git2/deprecated.h
@@ -777,6 +777,12 @@ typedef git_trace_cb git_trace_callback;
  */
 /**@{*/
 
+#ifndef GIT_EXPERIMENTAL_SHA256
+# define GIT_OID_RAWSZ    GIT_OID_SHA1_SIZE
+# define GIT_OID_HEXSZ    GIT_OID_SHA1_HEXSIZE
+# define GIT_OID_HEX_ZERO GIT_OID_SHA1_HEXZERO
+#endif
+
 GIT_EXTERN(int) git_oid_iszero(const git_oid *id);
 
 /**@}*/
diff --git a/include/git2/oid.h b/include/git2/oid.h
index 6136e2858..3e828ae70 100644
--- a/include/git2/oid.h
+++ b/include/git2/oid.h
@@ -9,6 +9,7 @@
 
 #include "common.h"
 #include "types.h"
+#include "experimental.h"
 
 /**
  * @file git2/oid.h
@@ -21,22 +22,74 @@ GIT_BEGIN_DECL
 
 /** The type of object id. */
 typedef enum {
+
+#ifdef GIT_EXPERIMENTAL_SHA256
 	GIT_OID_SHA1 = 1,  /**< SHA1 */
 	GIT_OID_SHA256 = 2 /**< SHA256 */
+#else
+	GIT_OID_SHA1 = 1   /**< SHA1 */
+#endif
+
 } git_oid_t;
 
+/*
+ * SHA1 is currently the only supported object ID type.
+ */
+
 /** SHA1 is currently libgit2's default oid type. */
 #define GIT_OID_DEFAULT         GIT_OID_SHA1
 
-/** Size (in bytes) of a raw/binary oid */
+/** Size (in bytes) of a raw/binary sha1 oid */
 #define GIT_OID_SHA1_SIZE       20
-#define GIT_OID_SHA256_SIZE     32
-#define GIT_OID_MAX_SIZE        GIT_OID_SHA256_SIZE
-
-/** Size (in bytes) of a hex formatted oid */
+/** Size (in bytes) of a hex formatted sha1 oid */
 #define GIT_OID_SHA1_HEXSIZE   (GIT_OID_SHA1_SIZE * 2)
-#define GIT_OID_SHA256_HEXSIZE (GIT_OID_SHA256_SIZE * 2)
-#define GIT_OID_MAX_HEXSIZE     GIT_OID_SHA256_HEXSIZE
+
+/**
+ * The binary representation of the null sha1 object ID.
+ */
+#ifndef GIT_EXPERIMENTAL_SHA256
+# define GIT_OID_SHA1_ZERO   { { 0 } }
+#else
+# define GIT_OID_SHA1_ZERO   { GIT_OID_SHA1, { 0 } }
+#endif
+
+/**
+ * The string representation of the null sha1 object ID.
+ */
+#define GIT_OID_SHA1_HEXZERO   "0000000000000000000000000000000000000000"
+
+/*
+ * Experimental SHA256 support is a breaking change to the API.
+ * This exists for application compatibility testing.
+ */
+
+#ifdef GIT_EXPERIMENTAL_SHA256
+
+/** Size (in bytes) of a raw/binary sha256 oid */
+# define GIT_OID_SHA256_SIZE     32
+/** Size (in bytes) of a hex formatted sha256 oid */
+# define GIT_OID_SHA256_HEXSIZE (GIT_OID_SHA256_SIZE * 2)
+
+/**
+ * The binary representation of the null sha256 object ID.
+ */
+# define GIT_OID_SHA256_ZERO { GIT_OID_SHA256, { 0 } }
+
+/**
+ * The string representation of the null sha256 object ID.
+ */
+# define GIT_OID_SHA256_HEXZERO "0000000000000000000000000000000000000000000000000000000000000000"
+
+#endif
+
+/* Maximum possible object ID size in raw / hex string format. */
+#ifndef GIT_EXPERIMENTAL_SHA256
+# define GIT_OID_MAX_SIZE        GIT_OID_SHA1_SIZE
+# define GIT_OID_MAX_HEXSIZE     GIT_OID_SHA1_HEXSIZE
+#else
+# define GIT_OID_MAX_SIZE        GIT_OID_SHA256_SIZE
+# define GIT_OID_MAX_HEXSIZE     GIT_OID_SHA256_HEXSIZE
+#endif
 
 /** Minimum length (in number of hex characters,
  * i.e. packets of 4 bits) of an oid prefix */
@@ -44,25 +97,16 @@ typedef enum {
 
 /** Unique identity of any object (commit, tree, blob, tag). */
 typedef struct git_oid {
+
+#ifdef GIT_EXPERIMENTAL_SHA256
 	/** type of object id */
 	unsigned char type;
+#endif
 
 	/** raw binary formatted id */
 	unsigned char id[GIT_OID_MAX_SIZE];
 } git_oid;
 
-/**
- * The binary representation of the null object ID.
- */
-#define GIT_OID_SHA1_ZERO   { GIT_OID_SHA1,   { 0 } }
-#define GIT_OID_SHA256_ZERO { GIT_OID_SHA256, { 0 } }
-
-/**
- * The string representation of the null object ID.
- */
-#define GIT_OID_SHA1_HEXZERO   "0000000000000000000000000000000000000000"
-#define GIT_OID_SHA256_HEXZERO "0000000000000000000000000000000000000000000000000000000000000000"
-
 /**
  * Parse a hex formatted object id into a git_oid.
  *
diff --git a/src/cli/CMakeLists.txt b/src/cli/CMakeLists.txt
index 5274ab086..46f4d63b5 100644
--- a/src/cli/CMakeLists.txt
+++ b/src/cli/CMakeLists.txt
@@ -1,5 +1,7 @@
 set(CLI_INCLUDES
 	"${libgit2_BINARY_DIR}/src/util"
+	"${libgit2_BINARY_DIR}/include"
+	"${libgit2_BINARY_DIR}/include/git2"
 	"${libgit2_SOURCE_DIR}/src/util"
 	"${libgit2_SOURCE_DIR}/src/cli"
 	"${libgit2_SOURCE_DIR}/include")
@@ -39,6 +41,7 @@ target_link_libraries(git2_cli ${CLI_LIBGIT2_LIBRARY} ${LIBGIT2_SYSTEM_LIBS})
 
 set_target_properties(git2_cli PROPERTIES C_STANDARD 90)
 set_target_properties(git2_cli PROPERTIES RUNTIME_OUTPUT_DIRECTORY ${libgit2_BINARY_DIR})
+set_target_properties(git2_cli PROPERTIES OUTPUT_NAME ${LIBGIT2_FILENAME})
 
 ide_split_sources(git2_cli)
 
diff --git a/src/libgit2/CMakeLists.txt b/src/libgit2/CMakeLists.txt
index 5fbb03d9f..3462b795e 100644
--- a/src/libgit2/CMakeLists.txt
+++ b/src/libgit2/CMakeLists.txt
@@ -9,6 +9,8 @@ include(PkgBuildConfig)
 
 set(LIBGIT2_INCLUDES
 	"${PROJECT_BINARY_DIR}/src/util"
+	"${PROJECT_BINARY_DIR}/include"
+	"${PROJECT_BINARY_DIR}/include/git2"
 	"${PROJECT_SOURCE_DIR}/src/libgit2"
 	"${PROJECT_SOURCE_DIR}/src/util"
 	"${PROJECT_SOURCE_DIR}/include")
@@ -109,7 +111,7 @@ if(SONAME)
 	endif()
 endif()
 
-pkg_build_config(NAME libgit2
+pkg_build_config(NAME "${LIBGIT2_FILENAME}"
 	VERSION ${libgit2_VERSION}
 	DESCRIPTION "The git library, take 2"
 	LIBS_SELF git2
@@ -122,10 +124,26 @@ if(MSVC_IDE)
 	set_source_files_properties(win32/precompiled.c COMPILE_FLAGS "/Ycprecompiled.h")
 endif()
 
+# support experimental features and functionality
+
+configure_file(experimental.h.in "${PROJECT_BINARY_DIR}/include/git2/experimental.h")
+
+# translate filenames in the git2.h so that they match the install directory
+# (allows for side-by-side installs of libgit2 and libgit2-experimental.)
+
+FILE(READ "${PROJECT_SOURCE_DIR}/include/git2.h" LIBGIT2_INCLUDE)
+STRING(REGEX REPLACE "#include \"git2\/" "#include \"${LIBGIT2_FILENAME}/" LIBGIT2_INCLUDE "${LIBGIT2_INCLUDE}")
+FILE(WRITE "${PROJECT_BINARY_DIR}/include/${LIBGIT2_FILENAME}.h" ${LIBGIT2_INCLUDE})
+
 # Install
+
 install(TARGETS libgit2package
 	RUNTIME DESTINATION ${CMAKE_INSTALL_BINDIR}
 	LIBRARY DESTINATION ${CMAKE_INSTALL_LIBDIR}
 	ARCHIVE DESTINATION ${CMAKE_INSTALL_LIBDIR})
-install(DIRECTORY ${PROJECT_SOURCE_DIR}/include/git2 DESTINATION ${CMAKE_INSTALL_INCLUDEDIR})
-install(FILES ${PROJECT_SOURCE_DIR}/include/git2.h DESTINATION ${CMAKE_INSTALL_INCLUDEDIR})
+install(DIRECTORY ${PROJECT_SOURCE_DIR}/include/git2/
+        DESTINATION "${CMAKE_INSTALL_INCLUDEDIR}/${LIBGIT2_FILENAME}")
+install(FILES ${PROJECT_BINARY_DIR}/include/git2/experimental.h
+        DESTINATION "${CMAKE_INSTALL_INCLUDEDIR}/${LIBGIT2_FILENAME}")
+install(FILES "${PROJECT_BINARY_DIR}/include/${LIBGIT2_FILENAME}.h"
+        DESTINATION ${CMAKE_INSTALL_INCLUDEDIR})
diff --git a/src/libgit2/diff.c b/src/libgit2/diff.c
index 91931e75b..20a18c4b9 100644
--- a/src/libgit2/diff.c
+++ b/src/libgit2/diff.c
@@ -381,7 +381,10 @@ int git_diff_patchid(git_oid *out, git_diff *diff, git_diff_patchid_options *opt
 	if ((error = (flush_hunk(&args.result, &args.ctx))) < 0)
 		goto out;
 
+#ifdef GIT_EXPERIMENTAL_SHA256
 	args.result.type = GIT_OID_SHA1;
+#endif
+
 	git_oid_cpy(out, &args.result);
 
 out:
diff --git a/src/libgit2/experimental.h.in b/src/libgit2/experimental.h.in
new file mode 100644
index 000000000..3d6e931e2
--- /dev/null
+++ b/src/libgit2/experimental.h.in
@@ -0,0 +1,6 @@
+#ifndef INCLUDE_experimental_h__
+#define INCLUDE_experimental_h__
+
+#cmakedefine GIT_EXPERIMENTAL_SHA256 1
+
+#endif
diff --git a/src/libgit2/indexer.c b/src/libgit2/indexer.c
index c35e659e5..ace73386c 100644
--- a/src/libgit2/indexer.c
+++ b/src/libgit2/indexer.c
@@ -444,7 +444,10 @@ static int store_object(git_indexer *idx)
 		git__free(pentry);
 		goto on_error;
 	}
+
+#ifdef GIT_EXPERIMENTAL_SHA256
 	oid.type = GIT_OID_SHA1;
+#endif
 
 	entry_size = idx->off - entry_start;
 	if (entry_start > UINT31_MAX) {
diff --git a/src/libgit2/object.c b/src/libgit2/object.c
index 3794e5c23..1e939384c 100644
--- a/src/libgit2/object.c
+++ b/src/libgit2/object.c
@@ -520,7 +520,10 @@ static int git_object__short_id(git_str *out, const git_object *obj)
 		memcpy(&id.id, &obj->cached.oid.id, (len + 1) / 2);
 		if (len & 1)
 			id.id[len / 2] &= 0xf0;
+
+#ifdef GIT_EXPERIMENTAL_SHA256
 		id.type = GIT_OID_SHA1;
+#endif
 
 		error = git_odb_exists_prefix(NULL, odb, &id, len);
 		if (error != GIT_EAMBIGUOUS)
@@ -635,7 +638,7 @@ int git_object__write_oid_header(
 	const char *header,
 	const git_oid *oid)
 {
-	size_t hex_size = git_oid_hexsize(oid->type);
+	size_t hex_size = git_oid_hexsize(git_oid_type(oid));
 	char hex_oid[GIT_OID_MAX_HEXSIZE];
 
 	if (!hex_size) {
diff --git a/src/libgit2/odb.c b/src/libgit2/odb.c
index b41ab4a03..00d68d6f4 100644
--- a/src/libgit2/odb.c
+++ b/src/libgit2/odb.c
@@ -140,7 +140,10 @@ int git_odb__hashobj(git_oid *id, git_rawobj *obj, git_oid_t oid_type)
 	vec[1].data = obj->data;
 	vec[1].len = obj->len;
 
+#ifdef GIT_EXPERIMENTAL_SHA256
 	id->type = oid_type;
+#endif
+
 	return git_hash_vec(id->id, vec, 2, algorithm);
 }
 
@@ -254,7 +257,10 @@ int git_odb__hashfd(
 	}
 
 	error = git_hash_final(out->id, &ctx);
+
+#ifdef GIT_EXPERIMENTAL_SHA256
 	out->type = oid_type;
+#endif
 
 done:
 	git_hash_ctx_cleanup(&ctx);
@@ -1332,7 +1338,7 @@ int git_odb_read(git_odb_object **out, git_odb *db, const git_oid *id)
 		error = odb_read_1(out, db, id, true);
 
 	if (error == GIT_ENOTFOUND)
-		return git_odb__error_notfound("no match for id", id, git_oid_hexsize(id->type));
+		return git_odb__error_notfound("no match for id", id, git_oid_hexsize(git_oid_type(id)));
 
 	return error;
 }
@@ -1679,7 +1685,10 @@ int git_odb_stream_finalize_write(git_oid *out, git_odb_stream *stream)
 			"stream_finalize_write()");
 
 	git_hash_final(out->id, stream->hash_ctx);
+
+#ifdef GIT_EXPERIMENTAL_SHA256
 	out->type = stream->oid_type;
+#endif
 
 	if (git_odb__freshen(stream->backend->odb, out))
 		return 0;
@@ -1858,8 +1867,8 @@ int git_odb__error_mismatch(const git_oid *expected, const git_oid *actual)
 	char expected_oid[GIT_OID_MAX_HEXSIZE + 1],
 	     actual_oid[GIT_OID_MAX_HEXSIZE + 1];
 
-	git_oid_tostr(expected_oid, git_oid_hexsize(expected->type) + 1, expected);
-	git_oid_tostr(actual_oid, git_oid_hexsize(actual->type) + 1, actual);
+	git_oid_tostr(expected_oid, git_oid_hexsize(git_oid_type(expected)) + 1, expected);
+	git_oid_tostr(actual_oid, git_oid_hexsize(git_oid_type(actual)) + 1, actual);
 
 	git_error_set(GIT_ERROR_ODB, "object hash mismatch - expected %s but got %s",
 		expected_oid, actual_oid);
diff --git a/src/libgit2/odb_loose.c b/src/libgit2/odb_loose.c
index f47ed50b8..49180bbd1 100644
--- a/src/libgit2/odb_loose.c
+++ b/src/libgit2/odb_loose.c
@@ -737,7 +737,9 @@ GIT_INLINE(int) filename_to_oid(struct loose_backend *backend, git_oid *oid, con
 		oid->id[1 + i/2] = (unsigned char) v;
 	}
 
+#ifdef GIT_EXPERIMENTAL_SHA256
 	oid->type = backend->options.oid_type;
+#endif
 
 	return 0;
 }
diff --git a/src/libgit2/oid.c b/src/libgit2/oid.c
index 7521dd27e..cea70c3b3 100644
--- a/src/libgit2/oid.c
+++ b/src/libgit2/oid.c
@@ -14,13 +14,13 @@
 #include <limits.h>
 
 const git_oid git_oid__empty_blob_sha1 =
-	{ GIT_OID_SHA1,
+	GIT_OID_INIT(GIT_OID_SHA1,
 	  { 0xe6, 0x9d, 0xe2, 0x9b, 0xb2, 0xd1, 0xd6, 0x43, 0x4b, 0x8b,
-	    0x29, 0xae, 0x77, 0x5a, 0xd8, 0xc2, 0xe4, 0x8c, 0x53, 0x91 }};
+	    0x29, 0xae, 0x77, 0x5a, 0xd8, 0xc2, 0xe4, 0x8c, 0x53, 0x91 });
 const git_oid git_oid__empty_tree_sha1 =
-	{ GIT_OID_SHA1,
+	GIT_OID_INIT(GIT_OID_SHA1,
 	  { 0x4b, 0x82, 0x5d, 0xc6, 0x42, 0xcb, 0x6e, 0xb9, 0xa0, 0x60,
-	    0xe5, 0x4b, 0xf8, 0xd6, 0x92, 0x88, 0xfb, 0xee, 0x49, 0x04 }};
+	    0xe5, 0x4b, 0xf8, 0xd6, 0x92, 0x88, 0xfb, 0xee, 0x49, 0x04 });
 
 static int oid_error_invalid(const char *msg)
 {
@@ -49,7 +49,9 @@ int git_oid_fromstrn(
 	if (length > git_oid_hexsize(type))
 		return oid_error_invalid("too long");
 
+#ifdef GIT_EXPERIMENTAL_SHA256
 	out->type = type;
+#endif
 	memset(out->id, 0, size);
 
 	for (p = 0; p < length; p++) {
@@ -82,7 +84,7 @@ int git_oid_nfmt(char *str, size_t n, const git_oid *oid)
 		return 0;
 	}
 
-	if (!(hex_size = git_oid_hexsize(oid->type)))
+	if (!(hex_size = git_oid_hexsize(git_oid_type(oid))))
 		return oid_error_invalid("unknown type");
 
 	if (n > hex_size) {
@@ -96,14 +98,14 @@ int git_oid_nfmt(char *str, size_t n, const git_oid *oid)
 
 int git_oid_fmt(char *str, const git_oid *oid)
 {
-	return git_oid_nfmt(str, git_oid_hexsize(oid->type), oid);
+	return git_oid_nfmt(str, git_oid_hexsize(git_oid_type(oid)), oid);
 }
 
 int git_oid_pathfmt(char *str, const git_oid *oid)
 {
 	size_t hex_size;
 
-	if (!(hex_size = git_oid_hexsize(oid->type)))
+	if (!(hex_size = git_oid_hexsize(git_oid_type(oid))))
 		return oid_error_invalid("unknown type");
 
 	git_oid_fmt_substr(str, oid, 0, 2);
@@ -115,13 +117,13 @@ int git_oid_pathfmt(char *str, const git_oid *oid)
 char *git_oid_tostr_s(const git_oid *oid)
 {
 	char *str = GIT_THREADSTATE->oid_fmt;
-	git_oid_nfmt(str, git_oid_hexsize(oid->type) + 1, oid);
+	git_oid_nfmt(str, git_oid_hexsize(git_oid_type(oid)) + 1, oid);
 	return str;
 }
 
 char *git_oid_allocfmt(const git_oid *oid)
 {
-	size_t hex_size = git_oid_hexsize(oid->type);
+	size_t hex_size = git_oid_hexsize(git_oid_type(oid));
 	char *str = git__malloc(hex_size + 1);
 
 	if (!hex_size || !str)
@@ -142,7 +144,7 @@ char *git_oid_tostr(char *out, size_t n, const git_oid *oid)
 	if (!out || n == 0)
 		return "";
 
-	hex_size = oid ? git_oid_hexsize(oid->type) : 0;
+	hex_size = oid ? git_oid_hexsize(git_oid_type(oid)) : 0;
 
 	if (n > hex_size + 1)
 		n = hex_size + 1;
@@ -160,7 +162,9 @@ int git_oid_fromraw(git_oid *out, const unsigned char *raw, git_oid_t type)
 	if (!(size = git_oid_size(type)))
 		return oid_error_invalid("unknown type");
 
+#ifdef GIT_EXPERIMENTAL_SHA256
 	out->type = type;
+#endif
 	memcpy(out->id, raw, size);
 	return 0;
 }
@@ -169,10 +173,13 @@ int git_oid_cpy(git_oid *out, const git_oid *src)
 {
 	size_t size;
 
-	if (!(size = git_oid_size(src->type)))
+	if (!(size = git_oid_size(git_oid_type(src))))
 		return oid_error_invalid("unknown type");
 
+#ifdef GIT_EXPERIMENTAL_SHA256
 	out->type = src->type;
+#endif
+
 	return git_oid_raw_cpy(out->id, src->id, size);
 }
 
@@ -188,8 +195,10 @@ int git_oid_equal(const git_oid *a, const git_oid *b)
 
 int git_oid_ncmp(const git_oid *oid_a, const git_oid *oid_b, size_t len)
 {
+#ifdef GIT_EXPERIMENTAL_SHA256
 	if (oid_a->type != oid_b->type)
 		return oid_a->type - oid_b->type;
+#endif
 
 	return git_oid_raw_ncmp(oid_a->id, oid_b->id, len);
 }
@@ -198,7 +207,7 @@ int git_oid_strcmp(const git_oid *oid_a, const char *str)
 {
 	const unsigned char *a;
 	unsigned char strval;
-	long size = (long)git_oid_size(oid_a->type);
+	long size = (long)git_oid_size(git_oid_type(oid_a));
 	int hexval;
 
 	for (a = oid_a->id; *str && (a - oid_a->id) < size; ++a) {
@@ -225,12 +234,14 @@ int git_oid_streq(const git_oid *oid_a, const char *str)
 int git_oid_is_zero(const git_oid *oid_a)
 {
 	const unsigned char *a = oid_a->id;
-	size_t size = git_oid_size(oid_a->type), i;
+	size_t size = git_oid_size(git_oid_type(oid_a)), i;
 
+#ifdef GIT_EXPERIMENTAL_SHA256
 	if (!oid_a->type)
 		return 1;
 	else if (!size)
 		return 0;
+#endif
 
 	for (i = 0; i < size; ++i, ++a)
 		if (*a != 0)
diff --git a/src/libgit2/oid.h b/src/libgit2/oid.h
index 64b6796c8..47d2327e9 100644
--- a/src/libgit2/oid.h
+++ b/src/libgit2/oid.h
@@ -9,21 +9,42 @@
 
 #include "common.h"
 
+#include "git2/experimental.h"
 #include "git2/oid.h"
 #include "hash.h"
 
-#define GIT_OID_NONE { 0, { 0 } }
+#ifdef GIT_EXPERIMENTAL_SHA256
+# define GIT_OID_NONE { 0, { 0 } }
+# define GIT_OID_INIT(type, ...) { type, __VA_ARGS__ }
+#else
+# define GIT_OID_NONE { { 0 } }
+# define GIT_OID_INIT(type, ...) { __VA_ARGS__ }
+#endif
 
 extern const git_oid git_oid__empty_blob_sha1;
 extern const git_oid git_oid__empty_tree_sha1;
 
+GIT_INLINE(git_oid_t) git_oid_type(const git_oid *oid)
+{
+#ifdef GIT_EXPERIMENTAL_SHA256
+	return oid->type;
+#else
+	GIT_UNUSED(oid);
+	return GIT_OID_SHA1;
+#endif
+}
+
 GIT_INLINE(size_t) git_oid_size(git_oid_t type)
 {
 	switch (type) {
 	case GIT_OID_SHA1:
 		return GIT_OID_SHA1_SIZE;
+
+#ifdef GIT_EXPERIMENTAL_SHA256
 	case GIT_OID_SHA256:
 		return GIT_OID_SHA256_SIZE;
+#endif
+
 	}
 
 	return 0;
@@ -34,8 +55,12 @@ GIT_INLINE(size_t) git_oid_hexsize(git_oid_t type)
 	switch (type) {
 	case GIT_OID_SHA1:
 		return GIT_OID_SHA1_HEXSIZE;
+
+#ifdef GIT_EXPERIMENTAL_SHA256
 	case GIT_OID_SHA256:
 		return GIT_OID_SHA256_HEXSIZE;
+#endif
+
 	}
 
 	return 0;
@@ -46,8 +71,12 @@ GIT_INLINE(git_hash_algorithm_t) git_oid_algorithm(git_oid_t type)
 	switch (type) {
 	case GIT_OID_SHA1:
 		return GIT_HASH_ALGORITHM_SHA1;
+
+#ifdef GIT_EXPERIMENTAL_SHA256
 	case GIT_OID_SHA256:
 		return GIT_HASH_ALGORITHM_SHA256;
+#endif
+
 	}
 
 	return 0;
@@ -142,16 +171,23 @@ GIT_INLINE(int) git_oid_raw_cpy(
  */
 GIT_INLINE(int) git_oid__cmp(const git_oid *a, const git_oid *b)
 {
+#ifdef GIT_EXPERIMENTAL_SHA256
 	if (a->type != b->type)
 		return a->type - b->type;
 
 	return git_oid_raw_cmp(a->id, b->id, git_oid_size(a->type));
+#else
+	return git_oid_raw_cmp(a->id, b->id, git_oid_size(GIT_OID_SHA1));
+#endif
 }
 
 GIT_INLINE(void) git_oid__cpy_prefix(
 	git_oid *out, const git_oid *id, size_t len)
 {
+#ifdef GIT_EXPERIMENTAL_SHA256
 	out->type = id->type;
+#endif
+
 	memcpy(&out->id, id->id, (len + 1) / 2);
 
 	if (len & 1)
@@ -173,7 +209,10 @@ GIT_INLINE(bool) git_oid__is_hexstr(const char *str, git_oid_t type)
 GIT_INLINE(void) git_oid_clear(git_oid *out, git_oid_t type)
 {
 	memset(out->id, 0, git_oid_size(type));
+
+#ifdef GIT_EXPERIMENTAL_SHA256
 	out->type = type;
+#endif
 }
 
 #endif
diff --git a/src/util/CMakeLists.txt b/src/util/CMakeLists.txt
index bf62870fb..b12ce409b 100644
--- a/src/util/CMakeLists.txt
+++ b/src/util/CMakeLists.txt
@@ -8,6 +8,8 @@ configure_file(git2_features.h.in git2_features.h)
 
 set(UTIL_INCLUDES
 	"${PROJECT_BINARY_DIR}/src/util"
+	"${PROJECT_BINARY_DIR}/include"
+	"${PROJECT_BINARY_DIR}/include/git2"
 	"${PROJECT_SOURCE_DIR}/src/util"
 	"${PROJECT_SOURCE_DIR}/include")
 
diff --git a/tests/clar/clar_libgit2.h b/tests/clar/clar_libgit2.h
index e0aff43ba..d2d9da0aa 100644
--- a/tests/clar/clar_libgit2.h
+++ b/tests/clar/clar_libgit2.h
@@ -5,6 +5,7 @@
 #include <git2.h>
 #include "common.h"
 #include "posix.h"
+#include "oid.h"
 
 /**
  * Replace for `clar_must_pass` that passes the last library error as the
@@ -140,17 +141,18 @@ GIT_INLINE(void) clar__assert_equal_oid(
 	if (git_oid_equal(one, two))
 		return;
 
-	if (one->type != two->type) {
+	if (git_oid_type(one) != git_oid_type(two)) {
 		char err[64];
 
-		snprintf(err, 64, "different oid types: %d vs %d", one->type, two->type);
+		snprintf(err, 64, "different oid types: %d vs %d", git_oid_type(one), git_oid_type(two));
 		clar__fail(file, func, line, desc, err, 1);
-	} else if (one->type == GIT_OID_SHA1) {
+	} else if (git_oid_type(one) == GIT_OID_SHA1) {
 		char err[] = "\"........................................\" != \"........................................\"";
 		git_oid_fmt(&err[1], one);
 		git_oid_fmt(&err[47], two);
 
 		clar__fail(file, func, line, desc, err, 1);
+#ifdef GIT_EXPERIMENTAL_SHA256
 	} else if (one->type == GIT_OID_SHA256) {
 		char err[] = "\"................................................................\" != \"................................................................\"";
 
@@ -158,6 +160,7 @@ GIT_INLINE(void) clar__assert_equal_oid(
 		git_oid_fmt(&err[71], one);
 
 		clar__fail(file, func, line, desc, err, 1);
+#endif
 	} else {
 		clar__fail(file, func, line, desc, "unknown oid types", 1);
 	}
diff --git a/tests/libgit2/core/oid.c b/tests/libgit2/core/oid.c
index f17054d55..dc93f738c 100644
--- a/tests/libgit2/core/oid.c
+++ b/tests/libgit2/core/oid.c
@@ -9,6 +9,7 @@ const char *str_oid_sha1 = "ae90f12eea699729ed24555e40b9fd669da12a12";
 const char *str_oid_sha1_p = "ae90f12eea699729ed";
 const char *str_oid_sha1_m = "ae90f12eea699729ed24555e40b9fd669da12a12THIS IS EXTRA TEXT THAT SHOULD GET IGNORED";
 
+#ifdef GIT_EXPERIMENTAL_SHA256
 static git_oid id_sha256;
 static git_oid idp_sha256;
 static git_oid idm_sha256;
@@ -16,6 +17,7 @@ static git_oid idm_sha256;
 const char *str_oid_sha256 = "d3e63d2f2e43d1fee23a74bf19a0ede156cba2d1bd602eba13de433cea1bb512";
 const char *str_oid_sha256_p = "d3e63d2f2e43d1fee2";
 const char *str_oid_sha256_m = "d3e63d2f2e43d1fee23a74bf19a0ede156cba2d1bd602eba13de433cea1bb512 GARBAGE EXTRA TEXT AT THE END";
+#endif
 
 void test_core_oid__initialize(void)
 {
@@ -23,9 +25,11 @@ void test_core_oid__initialize(void)
 	cl_git_pass(git_oid_fromstrp(&idp_sha1, str_oid_sha1_p, GIT_OID_SHA1));
 	cl_git_fail(git_oid_fromstrp(&idm_sha1, str_oid_sha1_m, GIT_OID_SHA1));
 
+#ifdef GIT_EXPERIMENTAL_SHA256
 	cl_git_pass(git_oid_fromstr(&id_sha256, str_oid_sha256, GIT_OID_SHA256));
 	cl_git_pass(git_oid_fromstrp(&idp_sha256, str_oid_sha256_p, GIT_OID_SHA256));
 	cl_git_fail(git_oid_fromstrp(&idm_sha256, str_oid_sha256_m, GIT_OID_SHA256));
+#endif
 }
 
 void test_core_oid__streq_sha1(void)
@@ -48,6 +52,7 @@ void test_core_oid__streq_sha1(void)
 
 void test_core_oid__streq_sha256(void)
 {
+#ifdef GIT_EXPERIMENTAL_SHA256
 	cl_assert_equal_i(0, git_oid_streq(&id_sha256, str_oid_sha256));
 	cl_assert_equal_i(-1, git_oid_streq(&id_sha256, "deadbeefdeadbeefdeadbeefdeadbeefdeadbeefdeadbeefdeadbeefdeadbeef"));
 
@@ -62,6 +67,7 @@ void test_core_oid__streq_sha256(void)
 
 	cl_assert_equal_i(-1, git_oid_streq(&idp_sha1, "deadbeef"));
 	cl_assert_equal_i(-1, git_oid_streq(&idp_sha1, "I'm not an oid.... :)"));
+#endif
 }
 
 void test_core_oid__strcmp_sha1(void)
@@ -84,6 +90,7 @@ void test_core_oid__strcmp_sha1(void)
 
 void test_core_oid__strcmp_sha256(void)
 {
+#ifdef GIT_EXPERIMENTAL_SHA256
 	cl_assert_equal_i(0, git_oid_strcmp(&id_sha256, str_oid_sha256));
 	cl_assert(git_oid_strcmp(&id_sha256, "deadbeefdeadbeefdeadbeefdeadbeefdeadbeefdeadbeefdeadbeefdeadbeef") < 0);
 
@@ -98,6 +105,7 @@ void test_core_oid__strcmp_sha256(void)
 
 	cl_assert(git_oid_strcmp(&idp_sha256, "deadbeef") < 0);
 	cl_assert_equal_i(-1, git_oid_strcmp(&idp_sha256, "I'm not an oid.... :)"));
+#endif
 }
 
 void test_core_oid__ncmp_sha1(void)
@@ -121,6 +129,7 @@ void test_core_oid__ncmp_sha1(void)
 
 void test_core_oid__ncmp_sha256(void)
 {
+#ifdef GIT_EXPERIMENTAL_SHA256
 	cl_assert(!git_oid_ncmp(&id_sha256, &idp_sha256, 0));
 	cl_assert(!git_oid_ncmp(&id_sha256, &idp_sha256, 1));
 	cl_assert(!git_oid_ncmp(&id_sha256, &idp_sha256, 2));
@@ -142,6 +151,7 @@ void test_core_oid__ncmp_sha256(void)
 	cl_assert(!git_oid_ncmp(&id_sha256, &id_sha256, 63));
 	cl_assert(!git_oid_ncmp(&id_sha256, &id_sha256, 64));
 	cl_assert(!git_oid_ncmp(&id_sha256, &id_sha256, 65));
+#endif
 }
 
 void test_core_oid__is_hexstr(void)
@@ -154,25 +164,25 @@ void test_core_oid__is_hexstr(void)
 
 void test_core_oid__fmt_substr_sha1(void)
 {
-	char buf[GIT_OID_MAX_HEXSIZE];
+	char buf[GIT_OID_MAX_HEXSIZE + 1];
 
-	memset(buf, 0, GIT_OID_MAX_HEXSIZE);
+	memset(buf, 0, GIT_OID_MAX_HEXSIZE + 1);
 	git_oid_fmt_substr(buf, &id_sha1, 0, 40);
 	cl_assert_equal_s(buf, str_oid_sha1);
 
-	memset(buf, 0, GIT_OID_MAX_HEXSIZE);
+	memset(buf, 0, GIT_OID_MAX_HEXSIZE + 1);
 	git_oid_fmt_substr(buf, &id_sha1, 0, 18);
 	cl_assert_equal_s(buf, str_oid_sha1_p);
 
-	memset(buf, 0, GIT_OID_MAX_HEXSIZE);
+	memset(buf, 0, GIT_OID_MAX_HEXSIZE + 1);
 	git_oid_fmt_substr(buf, &id_sha1, 0, 5);
 	cl_assert_equal_s(buf, "ae90f");
 
-	memset(buf, 0, GIT_OID_MAX_HEXSIZE);
+	memset(buf, 0, GIT_OID_MAX_HEXSIZE + 1);
 	git_oid_fmt_substr(buf, &id_sha1, 5, 5);
 	cl_assert_equal_s(buf, "12eea");
 
-	memset(buf, 0, GIT_OID_MAX_HEXSIZE);
+	memset(buf, 0, GIT_OID_MAX_HEXSIZE + 1);
 	git_oid_fmt_substr(buf, &id_sha1, 5, 6);
 	cl_assert_equal_s(buf, "12eea6");
 }
diff --git a/tests/libgit2/core/oidmap.c b/tests/libgit2/core/oidmap.c
index 317631c4e..34374ceef 100644
--- a/tests/libgit2/core/oidmap.c
+++ b/tests/libgit2/core/oidmap.c
@@ -28,7 +28,9 @@ void test_core_oidmap__initialize(void)
 		test_oids[i].oid.id[ 9] = (unsigned char)(i >> 8);
 		test_oids[i].oid.id[10] = (unsigned char)(i >> 16);
 		test_oids[i].oid.id[11] = (unsigned char)(i >> 24);
+#ifdef GIT_EXPERIMENTAL_SHA256
 		test_oids[i].oid.type = GIT_OID_SHA1;
+#endif
 	}
 
 	cl_git_pass(git_oidmap_new(&g_map));
@@ -94,9 +96,9 @@ void test_core_oidmap__get_fails_with_nonexisting_key(void)
 void test_core_oidmap__setting_oid_persists(void)
 {
 	git_oid oids[] = {
-	    { GIT_OID_SHA1, { 0x01 }},
-	    { GIT_OID_SHA1, { 0x02 }},
-	    { GIT_OID_SHA1, { 0x03 }}
+		GIT_OID_INIT(GIT_OID_SHA1, { 0x01 }),
+		GIT_OID_INIT(GIT_OID_SHA1, { 0x02 }),
+		GIT_OID_INIT(GIT_OID_SHA1, { 0x03 })
 	};
 
 	cl_git_pass(git_oidmap_set(g_map, &oids[0], "one"));
@@ -111,9 +113,9 @@ void test_core_oidmap__setting_oid_persists(void)
 void test_core_oidmap__setting_existing_key_updates(void)
 {
 	git_oid oids[] = {
-	    { GIT_OID_SHA1, { 0x01 }},
-	    { GIT_OID_SHA1, { 0x02 }},
-	    { GIT_OID_SHA1, { 0x03 }}
+		GIT_OID_INIT(GIT_OID_SHA1, { 0x01 }),
+		GIT_OID_INIT(GIT_OID_SHA1, { 0x02 }),
+		GIT_OID_INIT(GIT_OID_SHA1, { 0x03 })
 	};
 
 	cl_git_pass(git_oidmap_set(g_map, &oids[0], "one"));
diff --git a/tests/libgit2/core/pool.c b/tests/libgit2/core/pool.c
index 21aad3275..e16d85202 100644
--- a/tests/libgit2/core/pool.c
+++ b/tests/libgit2/core/pool.c
@@ -27,7 +27,12 @@ void test_core_pool__oid(void)
 
 #ifndef GIT_DEBUG_POOL
 	/* with fixed page size, allocation must end up with these values */
+
+# ifdef GIT_EXPERIMENTAL_SHA256
 	cl_assert_equal_i(sizeof(void *) == 8 ? 90 : 82, git_pool__open_pages(&p));
+# else
+	cl_assert_equal_i(sizeof(void *) == 8 ? 55 : 45, git_pool__open_pages(&p));
+# endif
 #endif
 	git_pool_clear(&p);
 }
diff --git a/tests/libgit2/odb/loose.c b/tests/libgit2/odb/loose.c
index 9f57a6866..9651ebab6 100644
--- a/tests/libgit2/odb/loose.c
+++ b/tests/libgit2/odb/loose.c
@@ -160,6 +160,7 @@ void test_odb_loose__exists_sha1(void)
 
 void test_odb_loose__exists_sha256(void)
 {
+#ifdef GIT_EXPERIMENTAL_SHA256
 	git_oid id, id2;
 	git_odb *odb;
 	git_odb_options odb_opts = GIT_ODB_OPTIONS_INIT;
@@ -184,6 +185,7 @@ void test_odb_loose__exists_sha256(void)
 	cl_assert_equal_i(GIT_ENOTFOUND, git_odb_exists_prefix(&id2, odb, &id, 8));
 
 	git_odb_free(odb);
+#endif
 }
 
 void test_odb_loose__simple_reads_sha1(void)
@@ -199,6 +201,7 @@ void test_odb_loose__simple_reads_sha1(void)
 
 void test_odb_loose__simple_reads_sha256(void)
 {
+#ifdef GIT_EXPERIMENTAL_SHA256
 	test_read_object(&commit_sha256);
 	test_read_object(&tree_sha256);
 	test_read_object(&tag_sha256);
@@ -206,6 +209,7 @@ void test_odb_loose__simple_reads_sha256(void)
 	test_read_object(&one_sha256);
 	test_read_object(&two_sha256);
 	test_read_object(&some_sha256);
+#endif
 }
 
 void test_odb_loose__streaming_reads_sha1(void)
@@ -226,6 +230,7 @@ void test_odb_loose__streaming_reads_sha1(void)
 
 void test_odb_loose__streaming_reads_sha256(void)
 {
+#ifdef GIT_EXPERIMENTAL_SHA256
 	size_t blocksizes[] = { 1, 2, 4, 16, 99, 1024, 123456789 };
 	size_t i;
 
@@ -238,6 +243,7 @@ void test_odb_loose__streaming_reads_sha256(void)
 		test_readstream_object(&two_sha256, blocksizes[i]);
 		test_readstream_object(&some_sha256, blocksizes[i]);
 	}
+#endif
 }
 
 void test_odb_loose__read_header_sha1(void)
@@ -253,6 +259,7 @@ void test_odb_loose__read_header_sha1(void)
 
 void test_odb_loose__read_header_sha256(void)
 {
+#ifdef GIT_EXPERIMENTAL_SHA256
 	test_read_header(&commit_sha256);
 	test_read_header(&tree_sha256);
 	test_read_header(&tag_sha256);
@@ -260,6 +267,7 @@ void test_odb_loose__read_header_sha256(void)
 	test_read_header(&one_sha256);
 	test_read_header(&two_sha256);
 	test_read_header(&some_sha256);
+#endif
 }
 
 static void test_write_object_permission(
diff --git a/tests/libgit2/odb/loose_data.h b/tests/libgit2/odb/loose_data.h
index 97681a014..1a830740d 100644
--- a/tests/libgit2/odb/loose_data.h
+++ b/tests/libgit2/odb/loose_data.h
@@ -35,6 +35,7 @@ static object_data one = {
     sizeof(one_data),
 };
 
+#ifdef GIT_EXPERIMENTAL_SHA256
 static object_data one_sha256 = {
     one_bytes,
     sizeof(one_bytes),
@@ -46,6 +47,7 @@ static object_data one_sha256 = {
     one_data,
     sizeof(one_data),
 };
+#endif
 
 
 /*
@@ -84,6 +86,7 @@ static unsigned char commit_bytes[] = {
     0x1f, 0x78, 0x35,
 };
 
+#ifdef GIT_EXPERIMENTAL_SHA256
 static unsigned char commit_bytes_sha256[] = {
     0x78, 0x01, 0x85, 0x90, 0xc1, 0x4e, 0xc3, 0x30,
     0x0c, 0x86, 0x39, 0xe7, 0x29, 0x7c, 0x87, 0x4e,
@@ -117,6 +120,7 @@ static unsigned char commit_bytes_sha256[] = {
     0x22, 0x98, 0x42, 0x6d, 0xcf, 0x7f, 0xbf, 0x83,
     0x7d, 0x03, 0x6d, 0x1e, 0x7e, 0xa9
 };
+#endif
 
 static unsigned char commit_data[] = {
     0x74, 0x72, 0x65, 0x65, 0x20, 0x64, 0x66, 0x66,
@@ -166,6 +170,7 @@ static unsigned char commit_data[] = {
     0x3e, 0x0a,
 };
 
+#ifdef GIT_EXPERIMENTAL_SHA256
 static unsigned char commit_data_sha256[] = {
     0x74, 0x72, 0x65, 0x65, 0x20, 0x33, 0x34, 0x61,
     0x34, 0x38, 0x35, 0x34, 0x62, 0x35, 0x34, 0x32,
@@ -216,6 +221,7 @@ static unsigned char commit_data_sha256[] = {
     0x6d, 0x70, 0x6c, 0x65, 0x2e, 0x63, 0x6f, 0x6d,
     0x3e, 0x0a
 };
+#endif
 
 static object_data commit = {
     commit_bytes,
@@ -229,6 +235,7 @@ static object_data commit = {
     sizeof(commit_data),
 };
 
+#ifdef GIT_EXPERIMENTAL_SHA256
 static object_data commit_sha256 = {
     commit_bytes_sha256,
     sizeof(commit_bytes_sha256),
@@ -240,6 +247,7 @@ static object_data commit_sha256 = {
     commit_data_sha256,
     sizeof(commit_data_sha256),
 };
+#endif
 
 /*
  * tree == dff2da90b254e1beb889d1f1f1288be1803782df (sha1)
@@ -284,6 +292,7 @@ static unsigned char tree_data[] = {
     0xd8, 0xc2, 0xe4, 0x8c, 0x53, 0x91,
 };
 
+#ifdef GIT_EXPERIMENTAL_SHA256
 static unsigned char tree_bytes_sha256[] = {
     0x78, 0x01, 0x2b, 0x29, 0x4a, 0x4d, 0x55, 0x30,
     0x32, 0x32, 0x66, 0x30, 0x34, 0x30, 0x30, 0x33,
@@ -346,6 +355,7 @@ static unsigned char tree_data_sha256[] = {
     0xa7, 0xcd, 0x2a, 0xc9, 0xb4, 0x4a, 0xda, 0xf7,
     0xed, 0x3e, 0xdc, 0x0d, 0x08, 0xdd, 0x78
 };
+#endif
 
 static object_data tree = {
     tree_bytes,
@@ -359,6 +369,7 @@ static object_data tree = {
     sizeof(tree_data),
 };
 
+#ifdef GIT_EXPERIMENTAL_SHA256
 static object_data tree_sha256 = {
     tree_bytes_sha256,
     sizeof(tree_bytes_sha256),
@@ -370,6 +381,7 @@ static object_data tree_sha256 = {
     tree_data_sha256,
     sizeof(tree_data_sha256),
 };
+#endif
 
 /*
  * tag == 09d373e1dfdc16b129ceec6dd649739911541e05 (sha1)
@@ -422,6 +434,7 @@ static unsigned char tag_data[] = {
     0x2e, 0x30, 0x2e, 0x31, 0x0a,
 };
 
+#ifdef GIT_EXPERIMENTAL_SHA256
 static unsigned char tag_bytes_sha256[] = {
     0x78, 0x01, 0x55, 0x8f, 0xd1, 0x4e, 0x84, 0x30,
     0x10, 0x45, 0x7d, 0xee, 0x57, 0xcc, 0xbb, 0x2e,
@@ -509,6 +522,7 @@ static unsigned char tag_data_sha256[] = {
     0x6d, 0x70, 0x6c, 0x65, 0x2e, 0x63, 0x6f, 0x6d,
     0x3e, 0x0a
 };
+#endif
 
 static object_data tag = {
     tag_bytes,
@@ -522,6 +536,7 @@ static object_data tag = {
     sizeof(tag_data),
 };
 
+#ifdef GIT_EXPERIMENTAL_SHA256
 static object_data tag_sha256 = {
     tag_bytes_sha256,
     sizeof(tag_bytes_sha256),
@@ -533,6 +548,7 @@ static object_data tag_sha256 = {
     tag_data_sha256,
     sizeof(tag_data_sha256),
 };
+#endif
 
 /*
  * zero == e69de29bb2d1d6434b8b29ae775ad8c2e48c5391 (sha1)
@@ -559,6 +575,7 @@ static object_data zero = {
     0,
 };
 
+#ifdef GIT_EXPERIMENTAL_SHA256
 static object_data zero_sha256 = {
     zero_bytes,
     sizeof(zero_bytes),
@@ -570,6 +587,7 @@ static object_data zero_sha256 = {
     zero_data,
     0,
 };
+#endif
 
 /*
  * two == 78981922613b2afb6025042ff6bd878ac1994e85 (sha1)
@@ -597,6 +615,7 @@ static object_data two = {
     sizeof(two_data),
 };
 
+#ifdef GIT_EXPERIMENTAL_SHA256
 static object_data two_sha256 = {
     two_bytes,
     sizeof(two_bytes),
@@ -608,6 +627,7 @@ static object_data two_sha256 = {
     two_data,
     sizeof(two_data),
 };
+#endif
 
 /*
  * some == fd8430bc864cfcd5f10e5590f8a447e01b942bfe (sha1)
@@ -858,6 +878,7 @@ static object_data some = {
     sizeof(some_data),
 };
 
+#ifdef GIT_EXPERIMENTAL_SHA256
 static object_data some_sha256 = {
     some_bytes,
     sizeof(some_bytes),
@@ -869,3 +890,4 @@ static object_data some_sha256 = {
     some_data,
     sizeof(some_data),
 };
+#endif