diff --git a/amp.module b/amp.module
index 4735775..a0fa390 100644
--- a/amp.module
+++ b/amp.module
@@ -340,10 +340,16 @@ function amp_url_inbound_alter(&$path, $original_path, $path_language) {
     case 'query_string':
       return;
     case 'suffix':
-      $non_amp_path = substr($path, 0, strlen($path) - strlen('/amp'));
+      $non_amp_path = $path;
+      if (substr($non_amp_path, -strlen('/amp')) == '/amp') {
+        $non_amp_path = substr($path, 0, strlen($path) - strlen('/amp'));
+      }
       break;
     case 'prefix':
-      $non_amp_path = substr($path, strlen('amp/'), strlen($path));
+      $non_amp_path = $path;
+      if (substr($non_amp_path, 0, strlen('amp/')) == 'amp/') {
+        $non_amp_path = substr($path, strlen('amp/'), strlen($path));
+      }
       break;
   }
   $system_path = drupal_lookup_path('source', $non_amp_path, $path_language);