diff --git a/browser/devtools/commandline/gcli.jsm b/browser/devtools/commandline/gcli.jsm
index 1a59a355124..a0e8d119de2 100644
--- a/browser/devtools/commandline/gcli.jsm
+++ b/browser/devtools/commandline/gcli.jsm
@@ -1172,6 +1172,8 @@ Argument.prototype.merge = function(following) {
  * - prefixPostSpace: Should the prefix be altered to end with a space?
  * - suffixSpace: Should the suffix be altered to end with a space?
  * - type: Constructor to use in creating new instances. Default: Argument
+ * - dontQuote: Should we avoid adding prefix/suffix quotes when the text value
+ *   has a space? Needed when we're completing a sub-command.
  */
 Argument.prototype.beget = function(options) {
   var text = this.text;
@@ -1182,10 +1184,13 @@ Argument.prototype.beget = function(options) {
     text = options.text;
 
     // We need to add quotes when the replacement string has spaces or is empty
-    var needsQuote = text.indexOf(' ') >= 0 || text.length == 0;
-    if (needsQuote && /['"]/.test(prefix)) {
-      prefix = prefix + '\'';
-      suffix = '\'' + suffix;
+    if (!options.dontQuote) {
+      var needsQuote = text.indexOf(' ') >= 0 || text.length == 0;
+      var hasQuote = /['"]$/.test(prefix);
+      if (needsQuote && !hasQuote) {
+        prefix = prefix + '\'';
+        suffix = '\'' + suffix;
+      }
     }
   }
 
@@ -1590,9 +1595,9 @@ NamedArgument.prototype.beget = function(options) {
   options.type = NamedArgument;
   var begotten = Argument.prototype.beget.call(this, options);
 
-  // Cut the prefix into |whitespace|non-whitespace|whitespace| so we can
+  // Cut the prefix into |whitespace|non-whitespace|whitespace+quote so we can
   // rebuild nameArg and valueArg from the parts
-  var matches = /^([\s]*)([^\s]*)([\s]*)$/.exec(begotten.prefix);
+  var matches = /^([\s]*)([^\s]*)([\s]*['"]?)$/.exec(begotten.prefix);
 
   if (this.valueArg == null && begotten.text === '') {
     begotten.nameArg = new Argument(matches[2], matches[1], matches[3]);
@@ -5822,7 +5827,10 @@ Requisition.prototype.complete = function(cursor, predictionChoice) {
   }
   else {
     // Mutate this argument to hold the completion
-    var arg = assignment.arg.beget({ text: prediction.name });
+    var arg = assignment.arg.beget({
+      text: prediction.name,
+      dontQuote: (assignment === this.commandAssignment)
+    });
     this.setAssignment(assignment, arg, { argUpdate: true });
 
     if (!prediction.incomplete) {
@@ -9983,9 +9991,7 @@ Completer.prototype.resized = function(ev) {
  * Bring the completion element up to date with what the requisition says
  */
 Completer.prototype.update = function(ev) {
-  if (ev && ev.choice != null) {
-    this.choice = ev.choice;
-  }
+  this.choice = (ev && ev.choice != null) ? ev.choice : 0;
 
   var data = this._getCompleterTemplateData();
   var template = this.template.cloneNode(true);
diff --git a/browser/devtools/commandline/test/browser_gcli_completion.js b/browser/devtools/commandline/test/browser_gcli_completion.js
index ba6389ea1ad..65347e16acc 100644
--- a/browser/devtools/commandline/test/browser_gcli_completion.js
+++ b/browser/devtools/commandline/test/browser_gcli_completion.js
@@ -407,5 +407,53 @@ exports.testCompleteIntoOptional = function(options) {
   });
 };
 
+exports.testSpaceComplete = function(options) {
+  helpers.setInput('tslong --sel2 wit');
+  helpers.check({
+    input:  'tslong --sel2 wit',
+    hints:                   'h space <msg> [options]',
+    markup: 'VVVVVVVIIIIIIVIII',
+    cursor: 17,
+    current: 'sel2',
+    status: 'ERROR',
+    tooltipState: 'true:importantFieldFlag',
+    args: {
+      command: { name: 'tslong' },
+      msg: { status: 'INCOMPLETE', message: '' },
+      num: { status: 'VALID' },
+      sel: { status: 'VALID' },
+      bool: { value: false, status: 'VALID' },
+      num2: { status: 'VALID' },
+      bool2: { value: false, status: 'VALID' },
+      sel2: { arg: ' --sel2 wit', status: 'INCOMPLETE' }
+    }
+  });
+
+  helpers.pressTab();
+  helpers.check({
+    input:  'tslong --sel2 \'with space\' ',
+    hints:                             '<msg> [options]',
+    markup: 'VVVVVVVVVVVVVVVVVVVVVVVVVVV',
+    cursor: 27,
+    current: 'sel2',
+    status: 'ERROR',
+    tooltipState: 'true:importantFieldFlag',
+    args: {
+      command: { name: 'tslong' },
+      msg: { status: 'INCOMPLETE', message: '' },
+      num: { status: 'VALID' },
+      sel: { status: 'VALID' },
+      bool: { value: false,status: 'VALID' },
+      num2: { status: 'VALID' },
+      bool2: { value: false,status: 'VALID' },
+      sel2: {
+        value: 'with space',
+        arg: ' --sel2 \'with space\' ',
+        status: 'VALID'
+      }
+    }
+  });
+};
+
 
 // });
diff --git a/browser/devtools/commandline/test/mockCommands.js b/browser/devtools/commandline/test/mockCommands.js
index eb2c88b84d2..d22173d7347 100644
--- a/browser/devtools/commandline/test/mockCommands.js
+++ b/browser/devtools/commandline/test/mockCommands.js
@@ -472,7 +472,7 @@ mockCommands.tslong = {
           name: 'sel2',
           type: {
             name: 'selection',
-            data: ['collapse', 'expand', 'end-expand', 'expand-strict']
+            data: [ 'collapse', 'basic', 'with space', 'with two spaces' ]
           },
           description: 'sel2 Desc',
           defaultValue: "collapse"