diff --git a/common/modules/io.jsm b/common/modules/io.jsm
index 53bc9257..fa24feae 100644
--- a/common/modules/io.jsm
+++ b/common/modules/io.jsm
@@ -841,7 +841,7 @@ unlet s:cpo_save
 
                 modules.autocommands.trigger("ShellCmdPost", {});
             }, {
-                argCount: "1",
+                argCount: "?",
                 bang: true,
                 // This is abominably slow.
                 // completer: function (context) completion.shellCommand(context),
diff --git a/common/tests/functional/testCommands.js b/common/tests/functional/testCommands.js
index 45e65e7f..86750083 100644
--- a/common/tests/functional/testCommands.js
+++ b/common/tests/functional/testCommands.js
@@ -45,7 +45,6 @@ function toolbarState(selector, state)
 
 var tests = {
     "!": {
-        error: [""],
         multiOutput: ["echo foo"]
     },
     get Clistkeys() this.listcommands,