diff --git a/prod/upload/combine.lua b/prod/upload/combine.lua
index 3d82946..4fb4971 100644
--- a/prod/upload/combine.lua
+++ b/prod/upload/combine.lua
@@ -15,11 +15,15 @@ for i = 1, len do
 end
 -- 从 nginx 变量取
 local magick = ngx.var.magick
+local convert = ngx.var.convert
 
 if not magick then
-    ngx.status = 500
-    ngx.say("image magick not found.")
-    return
+    if not convert then
+        ngx.status = 500
+        ngx.say("image magick not found.")
+        return
+    end
+    magick = ""
 end
 
 local result, _, code = os.execute(magick .. " convert -append " .. table.concat(origin, " ") .. " " .. combined)