diff --git a/pkgs/build-support/portable-service/default.nix b/pkgs/build-support/portable-service/default.nix
index 48237af5370f..c0baecb7b767 100644
--- a/pkgs/build-support/portable-service/default.nix
+++ b/pkgs/build-support/portable-service/default.nix
@@ -87,9 +87,9 @@ let
     };
 in
 
-assert lib.assertMsg (lib.all (
-  u: lib.hasPrefix pname u.name
-) units) "Unit names must be prefixed with the service name";
+assert
+  lib.all (u: lib.hasPrefix pname u.name) units
+  || throw "Unit names must be prefixed with the service name";
 
 stdenv.mkDerivation {
   pname = "${pname}-img";