diff --git a/src/addons/zmodem/zmodem.js b/src/addons/zmodem/zmodem.js
index 603e98cc..95e56460 100644
--- a/src/addons/zmodem/zmodem.js
+++ b/src/addons/zmodem/zmodem.js
@@ -19,12 +19,10 @@
     addon(window.Terminal);
   }
 })(function _zmodemAddon(Terminal) {
-    if (Terminal.prototype.attach) {
-        throw "The “zmodem” and “attach” addons are mutually incompatible.";
-    }
-
-    function _makeSendWsWrapper(socket) {
-        return 
+    for (let f of ["attach", "terminadoAttach"]) {
+        if (Terminal.prototype[f]) {
+            throw new Error(`The “zmodem” and “${f}” addons are mutually incompatible.`);
+        }
     }
 
     Object.assign(