diff --git a/pkgs/lib/sources.nix b/pkgs/lib/sources.nix
index 5a321bce708..6f8554d340b 100644
--- a/pkgs/lib/sources.nix
+++ b/pkgs/lib/sources.nix
@@ -10,7 +10,7 @@ rec {
   cleanSource =
     let filter = name: type: let baseName = baseNameOf (toString name); in ! (
       # Filter out Subversion and CVS directories.
-      (type == "directory" && (baseName == ".svn" || baseName == "CVS")) ||
+      (type == "directory" && (baseName == ".git" || baseName == ".svn" || baseName == "CVS")) ||
       # Filter out backup files.
       (lib.hasSuffix "~" baseName)
     );