diff --git a/pkgs/build-support/compress-drv/default.nix b/pkgs/build-support/compress-drv/default.nix
index 99eec034fb07..97f72d4fa396 100644
--- a/pkgs/build-support/compress-drv/default.nix
+++ b/pkgs/build-support/compress-drv/default.nix
@@ -64,9 +64,7 @@ let
     let
       matches = (builtins.length (builtins.split "\\{}" prog) - 1) / 2;
     in
-    lib.assertMsg (
-      matches == 1
-    ) "compressor ${ext} needs to have exactly one '{}', found ${toString matches}";
+    matches == 1 || throw "compressor ${ext} needs to have exactly one '{}', found ${toString matches}";
   mkCmd =
     ext: prog:
     assert validProg ext prog;