diff --git a/library/ssl_msg.c b/library/ssl_msg.c
index 51eb4619c6..6838a3b494 100644
--- a/library/ssl_msg.c
+++ b/library/ssl_msg.c
@@ -4798,6 +4798,9 @@ size_t mbedtls_ssl_get_bytes_avail( const mbedtls_ssl_context *ssl )
 
 int mbedtls_ssl_check_pending( const mbedtls_ssl_context *ssl )
 {
+    if( ssl == NULL || ssl->conf == NULL )
+        return( MBEDTLS_ERR_SSL_BAD_INPUT_DATA );
+
     /*
      * Case A: We're currently holding back
      * a message for further processing.