diff --git a/pkgs/tools/misc/poweralertd/default.nix b/pkgs/tools/misc/poweralertd/default.nix
index 4121b0712bd..58d54f5707b 100644
--- a/pkgs/tools/misc/poweralertd/default.nix
+++ b/pkgs/tools/misc/poweralertd/default.nix
@@ -13,7 +13,7 @@ stdenv.mkDerivation rec {
     sha256 = "19rw9q4pcqw56nmzjfglfikzx5wwjl4n08awwdhg0jy1k0bm3dvp";
   };
 
-  patchPhase = ''
+  postPatch = ''
     substituteInPlace meson.build --replace "systemd.get_pkgconfig_variable('systemduserunitdir')" "'${placeholder "out"}/lib/systemd/user'"
   '';