diff --git a/pkgs/build-support/fetchgithub/default.nix b/pkgs/build-support/fetchgithub/default.nix
index e12052e3d15d..3a232c735fe0 100644
--- a/pkgs/build-support/fetchgithub/default.nix
+++ b/pkgs/build-support/fetchgithub/default.nix
@@ -59,9 +59,8 @@ decorate (
   }@args:
 
   assert (
-    lib.assertMsg (lib.xor (tag == null) (
-      rev == null
-    )) "fetchFromGitHub requires one of either `rev` or `tag` to be provided (not both)."
+    lib.xor (tag == null) (rev == null)
+    || throw "fetchFromGitHub requires one of either `rev` or `tag` to be provided (not both)."
   );
 
   let