diff --git a/reactos/tools/fatten/fatten.c b/reactos/tools/fatten/fatten.c
index ef9d52c44b1..315e2933c43 100644
--- a/reactos/tools/fatten/fatten.c
+++ b/reactos/tools/fatten/fatten.c
@@ -45,7 +45,7 @@ DWORD get_fattime(void)
             timeinfo->tm_min,
             timeinfo->tm_hour,
             timeinfo->tm_mday,
-            timeinfo->tm_mon,
+            timeinfo->tm_mon  +  1,
             timeinfo->tm_year - 80,
         }
     };