diff --git a/wolfssl/wolfcrypt/wc_port.h b/wolfssl/wolfcrypt/wc_port.h
index fa8cbe093..7540e1714 100644
--- a/wolfssl/wolfcrypt/wc_port.h
+++ b/wolfssl/wolfcrypt/wc_port.h
@@ -34,7 +34,7 @@
 #endif
 
 /* detect C99 */
-#if defined(__STDC_VERSION__)
+#if !defined(WOLF_C99) && defined(__STDC_VERSION__)
     #if __STDC_VERSION__ >= 199901L
         #define WOLF_C99
     #endif