--- a/toolkit/components/extensions/Extension.jsm
+++ b/toolkit/components/extensions/Extension.jsm
@@ -1168,17 +1168,17 @@ class MockExtension {
           install.install();
         });
       });
     }
     throw new Error("installType must be one of: temporary, permanent");
   }
 
   shutdown() {
-    this.addon.uninstall(true);
+    this.addon.uninstall();
     return this.cleanupGeneratedFile();
   }
 
   cleanupGeneratedFile() {
     flushJarCache(this.file);
     return OS.File.remove(this.file.path);
   }
 }