diff --git a/tests/functions.sh b/tests/functions.sh
index 99af0e289..0718a6147 100644
--- a/tests/functions.sh
+++ b/tests/functions.sh
@@ -481,7 +481,7 @@ function ts_gen_diff {
 
 	if [ $? -ne 0 ] || [ -s $TS_DIFF ]; then
 		res=1
-		if [ "$TS_SHOWDIFF" == "yes" ]; then
+		if [ "$TS_SHOWDIFF" == "yes" -a "$TS_KNOWN_FAIL" != "yes" ]; then
 			echo
 			echo "diff-{{{"
 			cat $TS_DIFF