diff --git a/mozilla/extensions/cookie/nsPermissionManager.cpp b/mozilla/extensions/cookie/nsPermissionManager.cpp
index 10f161292ed..d80786577ff 100644
--- a/mozilla/extensions/cookie/nsPermissionManager.cpp
+++ b/mozilla/extensions/cookie/nsPermissionManager.cpp
@@ -56,17 +56,21 @@ class nsPermissionEnumerator : public nsISimpleEnumerator
           char *host;
           PRBool capability;
           PRInt32 type;
-          (void) PERMISSION_Enumerate
+          nsresult rv = PERMISSION_Enumerate
             (mHostCount, mTypeCount++, &host, &type, &capability);
-          if (mTypeCount == PERMISSION_TypeCount(mHostCount)) {
-            mTypeCount = 0;
-            mHostCount++;
+          if (NS_SUCCEEDED(rv)) {
+            if (mTypeCount == PERMISSION_TypeCount(mHostCount)) {
+              mTypeCount = 0;
+              mHostCount++;
+            }
+            nsIPermission *permission =
+              new nsPermission(host, type, capability);
+            *result = permission;
+            NS_ADDREF(*result);
+          } else {
+            *result = nsnull;
           }
-          nsIPermission *permission =
-            new nsPermission(host, type, capability);
-          *result = permission;
-          NS_ADDREF(*result);
-          return NS_OK;
+          return rv;
         }
 
         virtual ~nsPermissionEnumerator() 
diff --git a/mozilla/extensions/cookie/nsPermissions.cpp b/mozilla/extensions/cookie/nsPermissions.cpp
index 20b6ef2fdb1..33cf30128a6 100644
--- a/mozilla/extensions/cookie/nsPermissions.cpp
+++ b/mozilla/extensions/cookie/nsPermissions.cpp
@@ -555,9 +555,12 @@ PERMISSION_TypeCount(PRInt32 host) {
   return hostStruct->permissionList->Count();
 }
 
-PUBLIC void
+PUBLIC nsresult
 PERMISSION_Enumerate
     (PRInt32 hostNumber, PRInt32 typeNumber, char **host, PRInt32 *type, PRBool *capability) {
+  if (hostNumber > PERMISSION_HostCount()  || typeNumber > PERMISSION_TypeCount(hostNumber)) {
+    return NS_ERROR_FAILURE;
+  }
   permission_HostStruct *hostStruct;
   permission_TypeStruct * typeStruct;
 
@@ -571,6 +574,7 @@ PERMISSION_Enumerate
     (permission_TypeStruct*, hostStruct->permissionList->ElementAt(typeNumber));
   *capability = typeStruct->permission;
   *type = typeStruct->type;
+  return NS_OK;
 }
 
 PRIVATE void
diff --git a/mozilla/extensions/cookie/nsPermissions.h b/mozilla/extensions/cookie/nsPermissions.h
index d041e7313d2..8ceb0cd276a 100644
--- a/mozilla/extensions/cookie/nsPermissions.h
+++ b/mozilla/extensions/cookie/nsPermissions.h
@@ -44,7 +44,7 @@ extern void PERMISSION_DeletePersistentUserData(void);
 
 extern PRInt32 PERMISSION_HostCount();
 extern PRInt32 PERMISSION_TypeCount(PRInt32 host);
-extern void PERMISSION_Enumerate
+extern nsresult PERMISSION_Enumerate
   (PRInt32 hostNumber, PRInt32 typeNumber, char **host, PRInt32 *type, PRBool *capability);
 extern void PERMISSION_Remove(const char* host, PRInt32 type);