diff --git a/browser/base/content/browser.js b/browser/base/content/browser.js
index bdac8a8d19de..58f5674ecd6a 100644
--- a/browser/base/content/browser.js
+++ b/browser/base/content/browser.js
@@ -2281,18 +2281,17 @@ function BrowserTryToCloseWindow()
     window.close();     // WindowIsClosing does all the necessary checks
 }
 
-function loadURI(uri, referrer, postData, allowThirdPartyFixup)
-{
+function loadURI(uri, referrer, postData, allowThirdPartyFixup) {
+  if (postData === undefined)
+    postData = null;
+
+  var flags = nsIWebNavigation.LOAD_FLAGS_NONE;
+  if (allowThirdPartyFixup)
+    flags |= nsIWebNavigation.LOAD_FLAGS_ALLOW_THIRD_PARTY_FIXUP;
+
   try {
-    if (postData === undefined)
-      postData = null;
-    var flags = nsIWebNavigation.LOAD_FLAGS_NONE;
-    if (allowThirdPartyFixup) {
-      flags = nsIWebNavigation.LOAD_FLAGS_ALLOW_THIRD_PARTY_FIXUP;
-    }
     gBrowser.loadURIWithFlags(uri, flags, referrer, null, postData);
-  } catch (e) {
-  }
+  } catch (e) {}
 }
 
 function getShortcutOrURI(aURL, aPostDataRef, aMayInheritPrincipal) {
@@ -5647,7 +5646,8 @@ function middleMousePaste(event) {
   // bar's behavior (stripsurroundingwhitespace)
   clipboard = clipboard.replace(/\s*\n\s*/g, "");
 
-  let url = getShortcutOrURI(clipboard);
+  let mayInheritPrincipal = { value: false };
+  let url = getShortcutOrURI(clipboard, mayInheritPrincipal);
   try {
     makeURI(url);
   } catch (ex) {
@@ -5663,9 +5663,10 @@ function middleMousePaste(event) {
     Cu.reportError(ex);
   }
 
-  openUILink(url,
-             event,
-             true /* ignore the fact this is a middle click */);
+  // FIXME: Bug 631500, use openUILink directly
+  let where = whereToOpenLink(event, true);
+  openUILinkIn(url, where,
+               { disallowInheritPrincipal: !mayInheritPrincipal.value });
 
   event.stopPropagation();
 }
diff --git a/browser/base/content/test/Makefile.in b/browser/base/content/test/Makefile.in
index 724c6be831dd..dd7444851727 100644
--- a/browser/base/content/test/Makefile.in
+++ b/browser/base/content/test/Makefile.in
@@ -249,6 +249,7 @@ _BROWSER_FILES = \
                  test_wyciwyg_copying.html \
                  authenticate.sjs \
                  browser_minimize.js \
+                 browser_middleMouse_inherit.js \
                  $(NULL)
 
 ifneq (cocoa,$(MOZ_WIDGET_TOOLKIT))
diff --git a/browser/base/content/test/browser_middleMouse_inherit.js b/browser/base/content/test/browser_middleMouse_inherit.js
new file mode 100644
index 000000000000..121cb6da2e10
--- /dev/null
+++ b/browser/base/content/test/browser_middleMouse_inherit.js
@@ -0,0 +1,55 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+const middleMousePastePref = "middlemouse.contentLoadURL";
+const autoScrollPref = "general.autoScroll";
+function test() {
+  waitForExplicitFinish();
+
+  Services.prefs.setBoolPref(middleMousePastePref, true);
+  Services.prefs.setBoolPref(autoScrollPref, false);
+  let tab = gBrowser.selectedTab = gBrowser.addTab();
+
+  registerCleanupFunction(function () {
+    Services.prefs.clearUserPref(middleMousePastePref);
+    Services.prefs.clearUserPref(autoScrollPref);
+    gBrowser.removeTab(tab);
+  });
+
+  addPageShowListener(function () {
+    let pagePrincipal = gBrowser.contentPrincipal;
+
+    // copy javascript URI to the clipboard
+    let url = "javascript:1+1";
+    waitForClipboard(url,
+      function() {
+        Components.classes["@mozilla.org/widget/clipboardhelper;1"]
+                  .getService(Components.interfaces.nsIClipboardHelper)
+                  .copyString(url);
+      },
+      function () {
+        // Middle click on the content area
+        info("Middle clicking");
+        EventUtils.sendMouseEvent({type: "click", button: 1}, gBrowser);
+      },
+      function() {
+        ok(false, "Failed to copy URL to the clipboard");
+        finish();
+      }
+    );
+
+    addPageShowListener(function () {
+      is(gBrowser.currentURI.spec, url, "url loaded by middle click");
+      ok(!gBrowser.contentPrincipal.equals(pagePrincipal),
+         "middle click load of " + url + " should produce a page with a different principal");
+      finish();
+    });
+  });
+}
+
+function addPageShowListener(func) {
+  gBrowser.selectedBrowser.addEventListener("pageshow", function loadListener() {
+    gBrowser.selectedBrowser.removeEventListener("pageshow", loadListener, false);
+    func();
+  });
+}
diff --git a/browser/base/content/utilityOverlay.js b/browser/base/content/utilityOverlay.js
index 778d71d9a00f..e869f13c65a4 100644
--- a/browser/base/content/utilityOverlay.js
+++ b/browser/base/content/utilityOverlay.js
@@ -196,6 +196,7 @@ function openLinkIn(url, where, params) {
   var aReferrerURI          = params.referrerURI;
   var aRelatedToCurrent     = params.relatedToCurrent;
   var aInBackground         = params.inBackground;
+  var aDisallowInheritPrincipal = params.disallowInheritPrincipal;
 
   if (where == "save") {
     saveURL(url, null, null, true, null, aReferrerURI);
@@ -264,7 +265,12 @@ function openLinkIn(url, where, params) {
 
   switch (where) {
   case "current":
-    w.loadURI(url, aReferrerURI, aPostData, aAllowThirdPartyFixup);
+    let flags = Ci.nsIWebNavigation.LOAD_FLAGS_NONE;
+    if (aAllowThirdPartyFixup)
+      flags |= Ci.nsIWebNavigation.LOAD_FLAGS_ALLOW_THIRD_PARTY_FIXUP;
+    if (aDisallowInheritPrincipal)
+      flags |= Ci.nsIWebNavigation.LOAD_FLAGS_DISALLOW_INHERIT_OWNER;
+    w.gBrowser.loadURIWithFlags(url, flags, aReferrerURI, null, aPostData);
     break;
   case "tabshifted":
     loadInBackground = !loadInBackground;