diff --git a/src/lib/manifest.cpp b/src/lib/manifest.cpp
index 7a5cb08..d6871c4 100644
--- a/src/lib/manifest.cpp
+++ b/src/lib/manifest.cpp
@@ -131,6 +131,8 @@ list<string> Manifest::get_checksummed_files() {
       files.push_back( file );
     }
   }
+  files.sort();
+  files.unique();
   return files;
 }