diff --git a/include/mbedtls/check_config.h b/include/mbedtls/check_config.h
index 8c0c689..d31555d 100644
--- a/include/mbedtls/check_config.h
+++ b/include/mbedtls/check_config.h
@@ -362,7 +362,7 @@
 #error "MBEDTLS_RSA_C defined, but not all prerequisites"
 #endif
 
-#if defined(MBEDTLS_RSA_C) && ( !defined(MBEDTLS_PKCS1_V21) ||         \
+#if defined(MBEDTLS_RSA_C) && ( !defined(MBEDTLS_PKCS1_V21) &&         \
     !defined(MBEDTLS_PKCS1_V15) )
 #error "MBEDTLS_RSA_C defined, but none of the PKCS1 versions enabled"
 #endif