diff --git a/content/base/src/nsScriptLoader.cpp b/content/base/src/nsScriptLoader.cpp
index 6001d3329a9..030026db69f 100644
--- a/content/base/src/nsScriptLoader.cpp
+++ b/content/base/src/nsScriptLoader.cpp
@@ -120,7 +120,7 @@ public:
   nsString mScriptText;              // Holds script for loaded scripts
   PRUint32 mJSVersion;
   nsCOMPtr<nsIURI> mURI;
-  nsCOMPtr<nsIURI> mFinalURI;
+  nsCOMPtr<nsIPrincipal> mOriginPrincipal;
   PRInt32 mLineNo;
 };
 
@@ -882,8 +882,6 @@ nsScriptLoader::EvaluateScript(nsScriptLoadRequest* aRequest,
     return NS_ERROR_FAILURE;
   }
 
-  nsIURI* uri = aRequest->mFinalURI ? aRequest->mFinalURI : aRequest->mURI;
-
   bool oldProcessingScriptTag = context->GetProcessingScriptTag();
   context->SetProcessingScriptTag(true);
 
@@ -891,13 +889,15 @@ nsScriptLoader::EvaluateScript(nsScriptLoadRequest* aRequest,
   nsCOMPtr<nsIScriptElement> oldCurrent = mCurrentScript;
   mCurrentScript = aRequest->mElement;
 
+  // It's very important to use aRequest->mURI, not the final URI of the channel
+  // aRequest ended up getting script data from, as the script filename.
   nsCAutoString url;
-  nsContentUtils::GetWrapperSafeScriptFilename(mDocument, uri, url);
+  nsContentUtils::GetWrapperSafeScriptFilename(mDocument, aRequest->mURI, url);
 
   bool isUndefined;
   rv = context->EvaluateString(aScript, globalObject->GetGlobalJSObject(),
                                mDocument->NodePrincipal(),
-                               mDocument->NodePrincipal(),
+                               aRequest->mOriginPrincipal,
                                url.get(), aRequest->mLineNo,
                                aRequest->mJSVersion, nsnull, &isUndefined);
 
@@ -1214,7 +1214,10 @@ nsScriptLoader::PrepareLoadedRequest(nsScriptLoadRequest* aRequest,
   }
 
   nsCOMPtr<nsIChannel> channel = do_QueryInterface(req);
-  NS_GetFinalChannelURI(channel, getter_AddRefs(aRequest->mFinalURI));
+  rv = nsContentUtils::GetSecurityManager()->
+    GetChannelPrincipal(channel, getter_AddRefs(aRequest->mOriginPrincipal));
+  NS_ENSURE_SUCCESS(rv, rv);
+
   if (aStringLen) {
     // Check the charset attribute to determine script charset.
     nsAutoString hintCharset;
diff --git a/content/base/test/test_bug461735.html b/content/base/test/test_bug461735.html
index 3c08173ad3e..14cb247428b 100644
--- a/content/base/test/test_bug461735.html
+++ b/content/base/test/test_bug461735.html
@@ -19,7 +19,9 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=461735
 var errorFired = false;
 window.onerror = function(message, uri, line) {
   is(message, "Script error.", "Should have empty error message");
-  is(uri, "", "Should have empty error location URI");
+  is(uri,
+     "http://mochi.test:8888/tests/content/base/test/bug461735-redirect1.sjs",
+     "Should have pre-redirect error location URI");
   is(line, 0, "Shouldn't have a line here");
   errorFired = true;
 }
@@ -32,7 +34,9 @@ window.onerror = function(message, uri, line) {
 <script type="application/javascript">
 window.onerror = function(message, uri, line) {
   is(message, "c is not defined", "Should have correct error message");
-  is(uri, "http://mochi.test:8888/tests/content/base/test/bug461735-post-redirect.js", "Unexpected error location URI");
+  is(uri,
+     "http://mochi.test:8888/tests/content/base/test/bug461735-redirect2.sjs",
+     "Unexpected error location URI");
   is(line, 3, "Should have a line here");
   errorFired = true;
 }
diff --git a/dom/base/nsJSEnvironment.cpp b/dom/base/nsJSEnvironment.cpp
index a46896479f2..f63bf441802 100644
--- a/dom/base/nsJSEnvironment.cpp
+++ b/dom/base/nsJSEnvironment.cpp
@@ -89,6 +89,8 @@
 #include "nsGlobalWindow.h"
 #include "nsScriptNameSpaceManager.h"
 
+#include "nsJSPrincipals.h"
+
 #ifdef XP_MACOSX
 // AssertMacros.h defines 'check' and conflicts with AccessCheck.h
 #undef check
@@ -283,13 +285,15 @@ class ScriptErrorEvent : public nsRunnable
 {
 public:
   ScriptErrorEvent(nsIScriptGlobalObject* aScriptGlobal,
+                   nsIPrincipal* aScriptOriginPrincipal,
                    PRUint32 aLineNr, PRUint32 aColumn, PRUint32 aFlags,
                    const nsAString& aErrorMsg,
                    const nsAString& aFileName,
                    const nsAString& aSourceLine,
                    bool aDispatchEvent,
                    PRUint64 aInnerWindowID)
-  : mScriptGlobal(aScriptGlobal), mLineNr(aLineNr), mColumn(aColumn),
+    : mScriptGlobal(aScriptGlobal), mOriginPrincipal(aScriptOriginPrincipal),
+      mLineNr(aLineNr), mColumn(aColumn),
     mFlags(aFlags), mErrorMsg(aErrorMsg), mFileName(aFileName),
     mSourceLine(aSourceLine), mDispatchEvent(aDispatchEvent),
     mInnerWindowID(aInnerWindowID)
@@ -320,17 +324,11 @@ public:
           nsIPrincipal* p = sop->GetPrincipal();
           NS_ENSURE_STATE(p);
 
-          bool sameOrigin = mFileName.IsVoid();
+          bool sameOrigin = !mOriginPrincipal;
 
           if (p && !sameOrigin) {
-            nsCOMPtr<nsIURI> errorURI;
-            NS_NewURI(getter_AddRefs(errorURI), mFileName);
-            if (errorURI) {
-              // FIXME: Once error reports contain the origin of the
-              // error (principals) we should change this to do the
-              // security check based on the principals and not
-              // URIs. See bug 387476.
-              sameOrigin = NS_SUCCEEDED(p->CheckMayLoad(errorURI, false));
+            if (NS_FAILED(p->Subsumes(mOriginPrincipal, &sameOrigin))) {
+              sameOrigin = false;
             }
           }
 
@@ -342,13 +340,6 @@ public:
             NS_WARNING("Not same origin error!");
             errorevent.errorMsg = xoriginMsg.get();
             errorevent.lineNr = 0;
-            // FIXME: once the principal of the script is not tied to
-            // the filename, we can stop using the post-redirect
-            // filename if we want and remove this line.  Note that
-            // apparently we can't handle null filenames in the error
-            // event dispatching code.
-            static PRUnichar nullFilename[] = { PRUnichar(0) };
-            errorevent.fileName = nullFilename;
           }
 
           nsEventDispatcher::Dispatch(win, presContext, &errorevent, nsnull,
@@ -407,6 +398,7 @@ public:
 
 
   nsCOMPtr<nsIScriptGlobalObject> mScriptGlobal;
+  nsCOMPtr<nsIPrincipal>          mOriginPrincipal;
   PRUint32                        mLineNr;
   PRUint32                        mColumn;
   PRUint32                        mFlags;
@@ -502,8 +494,11 @@ NS_ScriptErrorReporter(JSContext *cx,
           innerWindowID = innerWin->WindowID();
         }
       }
+      JSPrincipals *prin = report->originPrincipals;
+      nsIPrincipal *principal =
+        prin ? static_cast<nsJSPrincipals*>(prin)->nsIPrincipalPtr : nsnull;
       nsContentUtils::AddScriptRunner(
-        new ScriptErrorEvent(globalObject, report->lineno,
+        new ScriptErrorEvent(globalObject, principal, report->lineno,
                              report->uctokenptr - report->uclinebuf,
                              report->flags, msg, fileName, sourceLine,
                              report->errorNumber != JSMSG_OUT_OF_MEMORY,
diff --git a/js/src/tests/js1_5/Regress/regress-328897.js b/js/src/tests/js1_5/Regress/regress-328897.js
index df51aa7a6a9..9724b8f052e 100644
--- a/js/src/tests/js1_5/Regress/regress-328897.js
+++ b/js/src/tests/js1_5/Regress/regress-328897.js
@@ -51,7 +51,7 @@ if (typeof window == 'undefined')
 }
 else
 {
-  expect = /(Script error.|uncaught exception: Permission denied to get property UnnamedClass.classes)/;
+  expect = /(Script error.|Permission denied for to get property XPCComponents.classes)/;
 
   window._onerror = window.onerror;
   window.onerror = (function (msg, page, line) {