diff --git a/browser/devtools/webconsole/test/browser.ini b/browser/devtools/webconsole/test/browser.ini
old mode 100755
new mode 100644
index 995202a86e4..2f9b850008b
--- a/browser/devtools/webconsole/test/browser.ini
+++ b/browser/devtools/webconsole/test/browser.ini
@@ -61,6 +61,7 @@ support-files =
   test-bug-859170-longstring-hang.html
   test-bug-869003-iframe.html
   test-bug-869003-top-window.html
+  test-closure-optimized-out.html
   test-closures.html
   test-console-assert.html
   test-console-count.html
@@ -137,6 +138,7 @@ support-files =
 [browser_console_native_getters.js]
 [browser_console_navigation_marker.js]
 [browser_console_nsiconsolemessage.js]
+[browser_console_optimized_out_vars.js]
 [browser_console_private_browsing.js]
 [browser_console_variables_view.js]
 [browser_console_variables_view_while_debugging.js]
diff --git a/browser/devtools/webconsole/test/browser_console_optimized_out_vars.js b/browser/devtools/webconsole/test/browser_console_optimized_out_vars.js
new file mode 100644
index 00000000000..92f7bc8bce4
--- /dev/null
+++ b/browser/devtools/webconsole/test/browser_console_optimized_out_vars.js
@@ -0,0 +1,82 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+// Check that inspecting an optimized out variable works when execution is
+// paused.
+
+function test() {
+  Task.spawn(function* () {
+    const TEST_URI = "http://example.com/browser/browser/devtools/webconsole/test/test-closure-optimized-out.html";
+    let {tab} = yield loadTab(TEST_URI);
+    let hud = yield openConsole(tab);
+    let { toolbox, panel, panelWin } = yield openDebugger();
+
+    yield waitForThreadEvents(panel, "resumed");
+    ok(true, "Debugger resumed");
+
+    let sources = panelWin.DebuggerView.Sources;
+    yield panel.addBreakpoint({ url: sources.values[0], line: 18 });
+    yield ensureThreadClientState(panel, "resumed");
+
+    let fetchedScopes = panelWin.once(panelWin.EVENTS.FETCHED_SCOPES);
+    let button = content.document.querySelector("button");
+    ok(button, "Button element found");
+    // Spin the event loop before causing the debuggee to pause, to allow
+    // this function to return first.
+    executeSoon(() => button.click());
+
+    let packet = yield fetchedScopes;
+    ok(true, "Scopes were fetched");
+
+    yield toolbox.selectTool("webconsole");
+
+    // This is the meat of the test: evaluate the optimized out variable.
+    hud.jsterm.execute("upvar");
+    yield waitForMessages({
+            webconsole: hud,
+            messages: [{
+              text: "optimized out",
+              category: CATEGORY_OUTPUT,
+            }]
+          });
+
+    finishTest();
+  }).then(null, aError => {
+    ok(false, "Got an error: " + aError.message + "\n" + aError.stack);
+  });
+}
+
+// Debugger helper functions stolen from browser/devtools/debugger/test/head.js.
+
+function ensureThreadClientState(aPanel, aState) {
+  let thread = aPanel.panelWin.gThreadClient;
+  let state = thread.state;
+
+  info("Thread is: '" + state + "'.");
+
+  if (state == aState) {
+    return promise.resolve(null);
+  } else {
+    return waitForThreadEvents(aPanel, aState);
+  }
+}
+
+function waitForThreadEvents(aPanel, aEventName, aEventRepeat = 1) {
+  info("Waiting for thread event: '" + aEventName + "' to fire: " + aEventRepeat + " time(s).");
+
+  let deferred = promise.defer();
+  let thread = aPanel.panelWin.gThreadClient;
+  let count = 0;
+
+  thread.addListener(aEventName, function onEvent(aEventName, ...aArgs) {
+    info("Thread event '" + aEventName + "' fired: " + (++count) + " time(s).");
+
+    if (count == aEventRepeat) {
+      ok(true, "Enough '" + aEventName + "' thread events have been fired.");
+      thread.removeListener(aEventName, onEvent);
+      deferred.resolve.apply(deferred, aArgs);
+    }
+  });
+
+  return deferred.promise;
+}
diff --git a/browser/devtools/webconsole/test/browser_webconsole_bug_1006027_message_timestamps_incorrect.js b/browser/devtools/webconsole/test/browser_webconsole_bug_1006027_message_timestamps_incorrect.js
old mode 100755
new mode 100644
diff --git a/browser/devtools/webconsole/test/test-closure-optimized-out.html b/browser/devtools/webconsole/test/test-closure-optimized-out.html
new file mode 100644
index 00000000000..3ad4e8fc0a0
--- /dev/null
+++ b/browser/devtools/webconsole/test/test-closure-optimized-out.html
@@ -0,0 +1,34 @@
+<!DOCTYPE HTML>
+<html>
+  <head>
+    <meta charset='utf-8'/>
+    <title>Debugger Test for Inspecting Optimized-Out Variables</title>
+    <!-- Any copyright is dedicated to the Public Domain.
+         http://creativecommons.org/publicdomain/zero/1.0/ -->
+    <script type="text/javascript">
+      window.addEventListener("load", function onload() {
+        window.removeEventListener("load", onload);
+        function clickHandler(event) {
+          button.removeEventListener("click", clickHandler, false);
+          function outer(arg) {
+            var upvar = arg * 2;
+            // The inner lambda only aliases arg, so the frontend alias analysis decides
+            // that upvar is not aliased and is not in the CallObject.
+            return function () {
+              arg += 2;
+            };
+          }
+
+          var f = outer(42);
+          f();
+        }
+        var button = document.querySelector("button");
+        button.addEventListener("click", clickHandler, false);
+      });
+    </script>
+
+  </head>
+  <body>
+    <button>Click me!</button>
+  </body>
+</html>