diff -r 000000000000 -r 6474c204b198 browser/components/sessionstore/test/browser_623779.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/browser/components/sessionstore/test/browser_623779.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,7 @@
+function test() {
+  gBrowser.pinTab(gBrowser.selectedTab);
+  var newTab = gBrowser.duplicateTab(gBrowser.selectedTab);
+  ok(!newTab.pinned, "duplicating a pinned tab creates unpinned tab");
+  gBrowser.removeTab(newTab);
+  gBrowser.unpinTab(gBrowser.selectedTab);
+}