diff --git a/pkgs/by-name/ll/llama-swap/package.nix b/pkgs/by-name/ll/llama-swap/package.nix
index 94762b624033..fab218337285 100644
--- a/pkgs/by-name/ll/llama-swap/package.nix
+++ b/pkgs/by-name/ll/llama-swap/package.nix
@@ -62,7 +62,7 @@ buildGoModule (finalAttrs: {
 
   postPatch = ''
     substituteInPlace internal/process/process_command_forking_test.go \
-      --replace "#!/bin/bash" "#!${lib.getExe bash}"
+      --replace-fail "#!/bin/bash" "#!${lib.getExe bash}"
   '';
 
   preBuild = ''