diff --git a/pkgs/applications/version-management/fossil/default.nix b/pkgs/applications/version-management/fossil/default.nix
index ed1a637a0e22..d38710a98822 100644
--- a/pkgs/applications/version-management/fossil/default.nix
+++ b/pkgs/applications/version-management/fossil/default.nix
@@ -59,7 +59,7 @@ stdenv.mkDerivation (finalAttrs: {
 
   postInstall = ''
     installManPage fossil.1
-    installShellCompletion --name fossil.bash tools/fossil-autocomplete.bash
+    installShellCompletion --cmd fossil tools/fossil-autocomplete.{bash,zsh}
   '';
 
   meta = {