diff --git a/src/util/posix.h b/src/util/posix.h
index c8f8cd9d2..607aa9dce 100644
--- a/src/util/posix.h
+++ b/src/util/posix.h
@@ -104,6 +104,8 @@ typedef __int64 off64_t;
 typedef __haiku_std_int64 off64_t;
 #elif defined(__APPLE__)
 typedef __int64_t off64_t;
+#elif defined(_AIX)
+typedef long long off64_t;
 #else
 typedef int64_t off64_t;
 #endif