diff --git a/netwerk/base/src/ProxyAutoConfig.cpp b/netwerk/base/src/ProxyAutoConfig.cpp
index 5fbb4e15a4c9..3e6bec303b5d 100644
--- a/netwerk/base/src/ProxyAutoConfig.cpp
+++ b/netwerk/base/src/ProxyAutoConfig.cpp
@@ -586,6 +586,7 @@ ProxyAutoConfig::SetupJS()
 
   JSAutoRequest ar(mJSRuntime->Context());
 
+  sRunning = this;
   JSScript *script = JS_CompileScript(mJSRuntime->Context(),
                                       mJSRuntime->Global(),
                                       mPACScript.get(), mPACScript.Length(),
@@ -595,8 +596,10 @@ ProxyAutoConfig::SetupJS()
     nsString alertMessage(NS_LITERAL_STRING("PAC file failed to install from "));
     alertMessage += NS_ConvertUTF8toUTF16(mPACURI);
     PACLogToConsole(alertMessage);
+    sRunning = nullptr;
     return NS_ERROR_FAILURE;
   }
+  sRunning = nullptr;
 
   mJSRuntime->SetOK();
   nsString alertMessage(NS_LITERAL_STRING("PAC file installed from "));
diff --git a/netwerk/test/unit/test_protocolproxyservice.js b/netwerk/test/unit/test_protocolproxyservice.js
index cbd0887f9417..b03778464f59 100644
--- a/netwerk/test/unit/test_protocolproxyservice.js
+++ b/netwerk/test/unit/test_protocolproxyservice.js
@@ -597,7 +597,41 @@ function myipaddress_callback(pi)
   do_check_neq(pi.host, null);
   do_check_neq(pi.host, "127.0.0.1");
   do_check_neq(pi.host, "::1");
+  
+  run_myipaddress_test_2();
+}
 
+function run_myipaddress_test_2()
+{
+  // test that myIPAddress() can be used outside of the scope of
+  // FindProxyForURL(). bug 829646.
+
+  var pac = 'data:text/plain,' +
+            'var myaddr = myIpAddress(); ' +
+            'function FindProxyForURL(url, host) {' +
+            ' return "PROXY " + myaddr + ":5678";' +
+            '}';
+
+  var uri = ios.newURI("http://www.mozilla.org/", null, null);
+  prefs.setIntPref("network.proxy.type", 2);
+  prefs.setCharPref("network.proxy.autoconfig_url", pac);
+
+  var cb = new resolveCallback();
+  cb.nextFunction = myipaddress2_callback;
+  var req = pps.asyncResolve(uri, 0, cb);
+}
+
+function myipaddress2_callback(pi)
+{
+  do_check_neq(pi, null);
+  do_check_eq(pi.type, "http");
+  do_check_eq(pi.port, 5678);
+
+  // make sure we didn't return localhost
+  do_check_neq(pi.host, null);
+  do_check_neq(pi.host, "127.0.0.1");
+  do_check_neq(pi.host, "::1");
+  
   run_failed_script_test();
 }