diff --git a/include/mbedtls/platform_util.h b/include/mbedtls/platform_util.h
index 4d9fcb6..22ccc89 100644
--- a/include/mbedtls/platform_util.h
+++ b/include/mbedtls/platform_util.h
@@ -141,7 +141,7 @@
  */
 #if !defined(MBEDTLS_CHECK_RETURN)
 #if defined(__GNUC__)
-#define MBEDTLS_CHECK_RETURN __attribute__((warn_unused_result))
+#define MBEDTLS_CHECK_RETURN __attribute__((__warn_unused_result__))
 #elif defined(_MSC_VER) && _MSC_VER >= 1700
 #include <sal.h>
 #define MBEDTLS_CHECK_RETURN _Check_return_