diff --git a/library/constant_time_impl.h b/library/constant_time_impl.h
index 273d215..821e7cf 100644
--- a/library/constant_time_impl.h
+++ b/library/constant_time_impl.h
@@ -31,7 +31,7 @@
  * Disable -Wredundant-decls so that gcc does not warn about this. This is re-enabled
  * at the bottom of this file.
  */
-#if __GNUC__ > 4
+#if defined(MBEDTLS_COMPILER_IS_GCC) && (__GNUC__ > 4)
     #pragma GCC diagnostic push
     #pragma GCC diagnostic ignored "-Wredundant-decls"
 #endif