diff --git a/cddl/usr.sbin/dtrace/tests/tools/dtest.sh b/cddl/usr.sbin/dtrace/tests/tools/dtest.sh
index 83f7a6c875d..d2f3dc4ed8d 100755
--- a/cddl/usr.sbin/dtrace/tests/tools/dtest.sh
+++ b/cddl/usr.sbin/dtrace/tests/tools/dtest.sh
@@ -119,6 +119,10 @@ test stdout:
 --
 $(cat $STDOUT)
 --
+test stdout diff:
+--
+$(diff -u $EXOUT $STDOUT)
+--
 __EOF__
     fi
     if [ $(stat -f '%z' $STDERR) -gt 0 ]; then