1 files changed, 2 insertions, 0 deletions
diff --git a/strings/json_lib.c b/strings/json_lib.c
index cbf672f5887..f6b4f15732d 100644
--- a/strings/json_lib.c
+++ b/strings/json_lib.c
@@ -1645,6 +1645,8 @@ int json_escape(CHARSET_INFO *str_cs,
         return -1;
       }
     }
+    else /* c_len == 0, an illegal symbol. */
+      return -1;
   }
 
   return (int)(json - json_start);