diff --git a/src/libgit2/repository.c b/src/libgit2/repository.c
index 2859bd480..be938b5b9 100644
--- a/src/libgit2/repository.c
+++ b/src/libgit2/repository.c
@@ -1852,7 +1852,8 @@ static int check_repositoryformatversion(int *version, git_config *config)
 
 static const char *builtin_extensions[] = {
 	"noop",
-	"objectformat"
+	"objectformat",
+	"worktreeconfig",
 };
 
 static git_vector user_extensions = { 0, git__strcmp_cb };
diff --git a/tests/libgit2/core/opts.c b/tests/libgit2/core/opts.c
index 1aa095adf..cbef29f99 100644
--- a/tests/libgit2/core/opts.c
+++ b/tests/libgit2/core/opts.c
@@ -34,9 +34,10 @@ void test_core_opts__extensions_query(void)
 
 	cl_git_pass(git_libgit2_opts(GIT_OPT_GET_EXTENSIONS, &out));
 
-	cl_assert_equal_sz(out.count, 2);
+	cl_assert_equal_sz(out.count, 3);
 	cl_assert_equal_s("noop", out.strings[0]);
 	cl_assert_equal_s("objectformat", out.strings[1]);
+	cl_assert_equal_s("worktreeconfig", out.strings[2]);
 
 	git_strarray_dispose(&out);
 }
@@ -49,10 +50,11 @@ void test_core_opts__extensions_add(void)
 	cl_git_pass(git_libgit2_opts(GIT_OPT_SET_EXTENSIONS, in, ARRAY_SIZE(in)));
 	cl_git_pass(git_libgit2_opts(GIT_OPT_GET_EXTENSIONS, &out));
 
-	cl_assert_equal_sz(out.count, 3);
+	cl_assert_equal_sz(out.count, 4);
 	cl_assert_equal_s("foo", out.strings[0]);
 	cl_assert_equal_s("noop", out.strings[1]);
 	cl_assert_equal_s("objectformat", out.strings[2]);
+	cl_assert_equal_s("worktreeconfig", out.strings[3]);
 
 	git_strarray_dispose(&out);
 }
@@ -65,10 +67,11 @@ void test_core_opts__extensions_remove(void)
 	cl_git_pass(git_libgit2_opts(GIT_OPT_SET_EXTENSIONS, in, ARRAY_SIZE(in)));
 	cl_git_pass(git_libgit2_opts(GIT_OPT_GET_EXTENSIONS, &out));
 
-	cl_assert_equal_sz(out.count, 3);
+	cl_assert_equal_sz(out.count, 4);
 	cl_assert_equal_s("bar", out.strings[0]);
 	cl_assert_equal_s("baz", out.strings[1]);
 	cl_assert_equal_s("objectformat", out.strings[2]);
+	cl_assert_equal_s("worktreeconfig", out.strings[3]);
 
 	git_strarray_dispose(&out);
 }
@@ -81,11 +84,12 @@ void test_core_opts__extensions_uniq(void)
 	cl_git_pass(git_libgit2_opts(GIT_OPT_SET_EXTENSIONS, in, ARRAY_SIZE(in)));
 	cl_git_pass(git_libgit2_opts(GIT_OPT_GET_EXTENSIONS, &out));
 
-	cl_assert_equal_sz(out.count, 4);
+	cl_assert_equal_sz(out.count, 5);
 	cl_assert_equal_s("bar", out.strings[0]);
 	cl_assert_equal_s("foo", out.strings[1]);
 	cl_assert_equal_s("noop", out.strings[2]);
 	cl_assert_equal_s("objectformat", out.strings[3]);
+	cl_assert_equal_s("worktreeconfig", out.strings[4]);
 
 	git_strarray_dispose(&out);
 }