diff --git a/tests/tests-ish.bash b/tests/tests-ish.bash
index 9e0fd1ae..13fb98f3 100755
--- a/tests/tests-ish.bash
+++ b/tests/tests-ish.bash
@@ -329,7 +329,7 @@ fi
 echo
 
 run "ish: test option --debug-fd 100 sets debug fd"
-if ( exec 100>&2 && ish --debug-fd 100 -c "env" | grep "^IAMROOT_DEBUG_FD=100$" )
+if ( exec 100>&2 && ish --debug-fd 100 -c "env && readlink /proc/self/fd/100" | grep "^IAMROOT_DEBUG_FD=100$" )
 then
 	ok
 else