diff --git a/testsuite/tests/simplCore/should_run/T5997.hs b/testsuite/tests/simplCore/should_run/T5997.hs
index cd0f1dda8be2fb5100f06f4d7788e09d071b9f69..c4a708da9f6b461c96d1edcbb2fcf1d2cd0cd0de 100644
--- a/testsuite/tests/simplCore/should_run/T5997.hs
+++ b/testsuite/tests/simplCore/should_run/T5997.hs
@@ -2,6 +2,8 @@
 
 module Main where
 
+-- Stack overflow if the tail recursion does not work out properly
+
 incompleteBetaWorker :: Double -> Double
 incompleteBetaWorker _ = loop 1 1 1 1
   where