diff --git a/ext/mbstring/mbstring.c b/ext/mbstring/mbstring.c
index 7c0c3de2d68..ff1192737a6 100644
--- a/ext/mbstring/mbstring.c
+++ b/ext/mbstring/mbstring.c
@@ -1969,7 +1969,7 @@ PHP_FUNCTION(mb_convert_encoding)
 				zend_hash_move_forward(target_hash);
 				i--;
 			}
-			if ( !strlen(_from_encodings)) {
+			if (_from_encodings != NULL && !strlen(_from_encodings)) {
 				efree(_from_encodings);
 				_from_encodings = NULL;
 			}