diff --git a/pkgs/build-support/fetchgit/builder.sh b/pkgs/build-support/fetchgit/builder.sh
index e27a47e903b..8d4e17f4a0e 100644
--- a/pkgs/build-support/fetchgit/builder.sh
+++ b/pkgs/build-support/fetchgit/builder.sh
@@ -1,6 +1,7 @@
 # tested so far with:
 # - no revision specified and remote has a HEAD which is used
 # - revision specified and remote has a HEAD
+# - revision specified and remote without HEAD
 source $stdenv/setup
 
 header "exporting $url (rev $rev) into $out"