diff --git a/nix/modules/knot.nix b/nix/modules/knot.nix
--- a/nix/modules/knot.nix
+++ b/nix/modules/knot.nix
@@ -239,6 +239,7 @@ [receive]
               advertisePushOptions = true
           [uploadpack]
               allowFilter = true
+              allowReachableSHA1InWant = true
           EOF
           ${setMotd}
           chown -R ${cfg.gitUser}:${cfg.gitUser} "${cfg.stateDir}"