diff --git a/t/t9001-send-email.sh b/t/t9001-send-email.sh
index 062c703b28..806f06631d 100755
--- a/t/t9001-send-email.sh
+++ b/t/t9001-send-email.sh
@@ -522,6 +522,12 @@ Result: OK
 EOF
 "
 
+replace_variable_fields () {
+	sed	-e "s/^\(Date:\).*/\1 DATE-STRING/" \
+		-e "s/^\(Message-Id:\).*/\1 MESSAGE-ID-STRING/" \
+		-e "s/^\(X-Mailer:\).*/\1 X-MAILER-STRING/"
+}
+
 test_suppression () {
 	git send-email \
 		--dry-run \
@@ -529,10 +535,7 @@ test_suppression () {
 		--from="Example <from@example.com>" \
 		--to=to@example.com \
 		--smtp-server relay.example.com \
-		$patches |
-	sed	-e "s/^\(Date:\).*/\1 DATE-STRING/" \
-		-e "s/^\(Message-Id:\).*/\1 MESSAGE-ID-STRING/" \
-		-e "s/^\(X-Mailer:\).*/\1 X-MAILER-STRING/" \
+		$patches | replace_variable_fields \
 		>actual-suppress-$1${2+"-$2"} &&
 	test_cmp expected-suppress-$1${2+"-$2"} actual-suppress-$1${2+"-$2"}
 }