diff --git a/library/rsa.c b/library/rsa.c
index 9fc80cd..18fc702 100644
--- a/library/rsa.c
+++ b/library/rsa.c
@@ -596,7 +596,8 @@
     if( mode == MBEDTLS_RSA_PRIVATE && ctx->padding != MBEDTLS_RSA_PKCS_V15 )
         return( MBEDTLS_ERR_RSA_BAD_INPUT_DATA );
 
-    if( f_rng == NULL )
+    // We don't check p_rng because it won't be dereferenced here
+    if( f_rng == NULL || input == NULL || output == NULL )
         return( MBEDTLS_ERR_RSA_BAD_INPUT_DATA );
 
     olen = ctx->len;