diff --git a/ghc/tests/concurrent/should_run/conc021.hs b/ghc/tests/concurrent/should_run/conc021.hs
index 6d3fe0a540ce3319b96f554628a60c0694576aaa..cd41dd63c79fa32a29d83e89603ea87c00330a1d 100644
--- a/ghc/tests/concurrent/should_run/conc021.hs
+++ b/ghc/tests/concurrent/should_run/conc021.hs
@@ -1,3 +1,5 @@
 module PrelMain where
 
+-- !!! test for uncaught exception
+
 mainIO = error "wurble"