diff --git a/mozilla/docshell/base/nsWebShell.cpp b/mozilla/docshell/base/nsWebShell.cpp
index 2f35f8d1712..f51ff23e93f 100644
--- a/mozilla/docshell/base/nsWebShell.cpp
+++ b/mozilla/docshell/base/nsWebShell.cpp
@@ -506,7 +506,7 @@ nsWebShell::GetHistoryIndex(PRInt32& aResult)
 }
 
 NS_IMETHODIMP
-nsWebShell::GetURL(PRInt32 aIndex, const PRUnichar** aURLResult)
+nsWebShell::GetURL(PRInt32 aIndex, PRUnichar** aURLResult)
 {
    NS_ENSURE_STATE(mSessionHistory);
    NS_ENSURE_TRUE(!IsFrame(), NS_ERROR_FAILURE);
diff --git a/mozilla/docshell/base/nsWebShell.h b/mozilla/docshell/base/nsWebShell.h
index 61dbeead362..512963d9345 100644
--- a/mozilla/docshell/base/nsWebShell.h
+++ b/mozilla/docshell/base/nsWebShell.h
@@ -83,7 +83,7 @@ public:
     NS_IMETHOD GoTo(PRInt32 aHistoryIndex);
     NS_IMETHOD GetHistoryLength(PRInt32& aResult);
     NS_IMETHOD GetHistoryIndex(PRInt32& aResult);
-    NS_IMETHOD GetURL(PRInt32 aHistoryIndex, const PRUnichar** aURLResult);
+    NS_IMETHOD GetURL(PRInt32 aHistoryIndex, PRUnichar** aURLResult);
 
     // nsIWebShellContainer
     NS_IMETHOD SetHistoryState(nsISupports* aLayoutHistoryState);
diff --git a/mozilla/webshell/public/nsIWebShell.h b/mozilla/webshell/public/nsIWebShell.h
index b1e5d2c1a8f..fde40ab213b 100644
--- a/mozilla/webshell/public/nsIWebShell.h
+++ b/mozilla/webshell/public/nsIWebShell.h
@@ -131,7 +131,7 @@ public:
   NS_IMETHOD GoTo(PRInt32 aHistoryIndex) = 0;
   NS_IMETHOD GetHistoryLength(PRInt32& aResult) = 0;
   NS_IMETHOD GetHistoryIndex(PRInt32& aResult) = 0;
-  NS_IMETHOD GetURL(PRInt32 aHistoryIndex, const PRUnichar **aURLResult) = 0;
+  NS_IMETHOD GetURL(PRInt32 aHistoryIndex, PRUnichar **aURLResult) = 0;
 
   // SetToolBar
   // SetMenuBar
diff --git a/mozilla/webshell/tests/viewer/nsBrowserWindow.cpp b/mozilla/webshell/tests/viewer/nsBrowserWindow.cpp
index 9fc02b02abd..1485cd90629 100644
--- a/mozilla/webshell/tests/viewer/nsBrowserWindow.cpp
+++ b/mozilla/webshell/tests/viewer/nsBrowserWindow.cpp
@@ -819,8 +819,8 @@ nsBrowserWindow::DispatchMenuItem(PRInt32 aID)
       PRInt32 theIndex;
       nsCOMPtr<nsIWebShell> webShell(do_QueryInterface(mDocShell));
       webShell->GetHistoryIndex(theIndex);
-      const PRUnichar* theURL;
-      webShell->GetURL(theIndex,&theURL);
+      nsXPIDLString theURL;
+      webShell->GetURL(theIndex, getter_Copies(theURL));
       nsAutoString theString(theURL);
       mApp->ViewSource(theString);
       //XXX Find out how the string is allocated, and perhaps delete it...