diff --git a/library/threading.c b/library/threading.c
index 95ae8d1..3d7f61b 100644
--- a/library/threading.c
+++ b/library/threading.c
@@ -32,9 +32,9 @@
 #if !defined(_WIN32) && (defined(__unix__) || \
     (defined(__APPLE__) && defined(__MACH__)))
 #include <unistd.h>
-#if !defined(_POSIX_VERSION)
+#if !defined(_POSIX_VERSION) || 200112L > _POSIX_THREAD_SAFE_FUNCTIONS
 #define THREADING_USE_GMTIME
-#endif /* !_POSIX_VERSION */
+#endif /* !_POSIX_VERSION || 200112L > _POSIX_THREAD_SAFE_FUNCTIONS */
 #endif /* !_WIN32 && (__unix__ || (__APPLE__ && __MACH__)) */
 
 #if defined(MBEDTLS_THREADING_PTHREAD)