diff --git a/pkgs/development/node-packages/overrides.nix b/pkgs/development/node-packages/overrides.nix
index f3a450d28840..3c22331fe5a2 100644
--- a/pkgs/development/node-packages/overrides.nix
+++ b/pkgs/development/node-packages/overrides.nix
@@ -188,10 +188,12 @@ final: prev: {
   graphite-cli = prev."@withgraphite/graphite-cli".override {
     name = "graphite-cli";
     nativeBuildInputs = [ pkgs.installShellFiles ];
+    # 'gt completion' auto-detects zshell from environment variables:
+    # https://github.com/yargs/yargs/blob/2b6ba3139396b2e623aed404293f467f16590039/lib/completion.ts#L45
     postInstall = ''
       installShellCompletion --cmd gt \
         --bash <($out/bin/gt completion) \
-        --zsh <($out/bin/gt completion)
+        --zsh <(ZSH_NAME=zsh $out/bin/gt completion)
     '';
   };