diff --git a/browser/components/preferences/in-content/subdialogs.js b/browser/components/preferences/in-content/subdialogs.js
index 614d3319568..e0f06ac1819 100644
--- a/browser/components/preferences/in-content/subdialogs.js
+++ b/browser/components/preferences/in-content/subdialogs.js
@@ -37,6 +37,12 @@ let gSubDialog = {
     // Wait for the stylesheets injected during DOMContentLoaded to load before showing the dialog
     // otherwise there is a flicker of the stylesheet applying.
     this._frame.addEventListener("load", this._onLoad.bind(this));
+
+    chromeBrowser.addEventListener("unload", function(aEvent) {
+      if (aEvent.target.location.href != "about:blank") {
+        this.close();
+      }
+    }.bind(this), true);
   },
 
   uninit: function() {
diff --git a/browser/components/preferences/in-content/tests/browser_subdialogs.js b/browser/components/preferences/in-content/tests/browser_subdialogs.js
index cea481477b3..914a6273bfe 100644
--- a/browser/components/preferences/in-content/tests/browser_subdialogs.js
+++ b/browser/components/preferences/in-content/tests/browser_subdialogs.js
@@ -76,7 +76,7 @@ let gTests = [{
     dialog.document.documentElement.cancelDialog();
 
     let closingEvent = yield closingPromise;
-    ise(closingEvent.detail.button, "cancel", "closing event should indicate button was 'accept'");
+    ise(closingEvent.detail.button, "cancel", "closing event should indicate button was 'cancel'");
 
     yield deferredClose.promise;
     ise(rv.acceptCount, 0, "return value should NOT have been updated");
@@ -118,6 +118,22 @@ let gTests = [{
     ise(rv.acceptCount, 0, "return value should NOT have been updated");
   },
 },
+{
+  desc: "Check that 'back' navigation will close the dialog",
+  run: function* () {
+    let rv = { acceptCount: 0 };
+    let deferredClose = Promise.defer();
+    let dialogPromise = openAndLoadSubDialog(gDialogURL, null, rv,
+                                             (aEvent) => dialogClosingCallback(deferredClose, aEvent));
+    let dialog = yield dialogPromise;
+
+    info("cancelling the dialog");
+    content.gSubDialog._frame.goBack();
+
+    yield deferredClose.promise;
+    ise(rv.acceptCount, 0, "return value should NOT have been updated");
+  },
+},
 {
   desc: "Hitting escape in the dialog",
   run: function* () {