--- a/tests/test-grep
+++ b/tests/test-grep
@@ -20,3 +20,11 @@ hg commit -m 4 -u spam -d '4 0'
 hg grep port port
 hg grep --all -nu port port
 hg grep import port
+
+hg cp port port2
+hg commit -m 4 -u spam -d '5 0'
+echo '% follow'
+hg grep -f 'import$' port2
+echo deport >> port2
+hg commit -m 5 -u eggs -d '6 0'
+hg grep -f --all -nu port port2