diff --git a/library/platform_util.c b/library/platform_util.c
index 4e97e4d..3d5cb5b 100644
--- a/library/platform_util.c
+++ b/library/platform_util.c
@@ -131,3 +131,8 @@
 #endif /* _WIN32 && !EFIX64 && !EFI32 */
 }
 #endif /* MBEDTLS_HAVE_TIME_DATE && MBEDTLS_PLATFORM_GMTIME_R_ALT */
+
+#if defined(MBEDTLS_TEST_HOOKS)
+void (*mbedtls_test_hook_test_fail)( const char *, int, const char *);
+#endif /* MBEDTLS_TEST_HOOKS */
+