diff --git a/cJSON.c b/cJSON.c
index 75430780f4eaa5b2a7af44c27e989f2893484388..54e18375cd980af119391aca88438c584213d58c 100644
--- a/cJSON.c
+++ b/cJSON.c
@@ -406,7 +406,7 @@ CJSON_PUBLIC(char*) cJSON_SetValuestring(cJSON *object, const char *valuestring)
         return NULL;
     }
     /* return NULL if the object is corrupted */
-    if (object->valuestring == NULL)
+    if (object->valuestring == NULL || valuestring == NULL)
     {
         return NULL;
     }