diff --git a/library/threading.c b/library/threading.c
index 7a32e67..fa4f6c9 100644
--- a/library/threading.c
+++ b/library/threading.c
@@ -29,6 +29,14 @@
 
 #include "mbedtls/threading.h"
 
+#if !defined(_WIN32) && (defined(__unix__) || \
+    (defined(__APPLE__) && defined(__MACH__)))
+#include <unistd.h>
+#if !defined(_POSIX_VERSION)
+#define MBEDTLS_THREADING_USE_GMTIME
+#endif /* !_POSIX_VERSION */
+#endif /* !_WIN32 && (__unix__ || (__APPLE__ && __MACH__)) */
+
 #if defined(MBEDTLS_THREADING_PTHREAD)
 static void threading_mutex_init_pthread( mbedtls_threading_mutex_t *mutex )
 {
@@ -114,6 +122,9 @@
 #if defined(MBEDTLS_FS_IO)
     mbedtls_mutex_init( &mbedtls_threading_readdir_mutex );
 #endif
+#if defined(MBEDTLS_THREADING_USE_GMTIME)
+    mbedtls_mutex_init( &mbedtls_threading_gmtime_mutex );
+#endif
 }
 
 /*
@@ -124,6 +135,9 @@
 #if defined(MBEDTLS_FS_IO)
     mbedtls_mutex_free( &mbedtls_threading_readdir_mutex );
 #endif
+#if defined(MBEDTLS_THREADING_USE_GMTIME)
+    mbedtls_mutex_free( &mbedtls_threading_gmtime_mutex );
+#endif
 }
 #endif /* MBEDTLS_THREADING_ALT */
 
@@ -136,5 +150,8 @@
 #if defined(MBEDTLS_FS_IO)
 mbedtls_threading_mutex_t mbedtls_threading_readdir_mutex MUTEX_INIT;
 #endif
+#if defined(MBEDTLS_THREADING_USE_GMTIME)
+mbedtls_threading_mutex_t mbedtls_threading_gmtime_mutex MUTEX_INIT;
+#endif
 
 #endif /* MBEDTLS_THREADING_C */