1 files changed, 17 insertions, 0 deletions
diff --git a/modules/libpref/test/unit/test_bug577950.js b/modules/libpref/test/unit/test_bug577950.js
new file mode 100644
index 0000000000..f9106a349f
--- /dev/null
+++ b/modules/libpref/test/unit/test_bug577950.js
@@ -0,0 +1,17 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+function run_test() {
+  var observer = {
+    QueryInterface: ChromeUtils.generateQI(["nsIObserver"]),
+
+    observe: function observe(aSubject, aTopic, aState) {
+      // Don't do anything.
+    },
+  };
+
+  /* Set the same pref twice.  This shouldn't leak. */
+  Services.prefs.addObserver("UserPref.nonexistent.setIntPref", observer);
+  Services.prefs.addObserver("UserPref.nonexistent.setIntPref", observer);
+}