diff --git a/src/Lookup.php b/src/Lookup.php
index 74370f8..98a8fe3 100644
--- a/src/Lookup.php
+++ b/src/Lookup.php
@@ -213,7 +213,7 @@ public function setUpgraderMap($map)
      */
     public function sanitiseNamespaces($class)
     {
-        return str_replace('\\', '.', ltrim($class, '\\'));
+        return preg_replace("/(\\\\+)/", '.', ltrim($class, '\\'));
     }
 
     /**
diff --git a/tests/LookupTest.php b/tests/LookupTest.php
index 3a658b7..43f667c 100644
--- a/tests/LookupTest.php
+++ b/tests/LookupTest.php
@@ -73,6 +73,10 @@ public function handleProvider()
                 array('q' => '\Already\Fully\Qualified', 'version' => '3.4'),
                 'http://mockserver/3.4/class-Already.Fully.Qualified.html'
             ),
+            array(
+                array('q' => '\\\\Already\\\\Fully\\\\Qualified', 'version' => '3.4'),
+                'http://mockserver/3.4/class-Already.Fully.Qualified.html'
+            ),
             array(
                 array('q' => 'Director', 'module' => 'framework'),
                 'http://mockserver/master/class-SilverStripe.Control.Director.html'