diff --git a/t/t4202-log.sh b/t/t4202-log.sh
index f1ea7d9..a093059 100755
--- a/t/t4202-log.sh
+++ b/t/t4202-log.sh
@@ -1692,7 +1692,7 @@
 	GNUPGHOME=. git log --graph --show-signature -n1 plain-nokey >actual &&
 	grep "^|\\\  merged tag" actual &&
 	grep "^| | gpg: Signature made" actual &&
-	grep "^| | gpg: Can'"'"'t check signature: \(public key not found\|No public key\)" actual
+	grep -E "^| | gpg: Can'"'"'t check signature: (public key not found|No public key)" actual
 '
 
 test_expect_success GPG 'log --graph --show-signature for merged tag with bad signature' '
diff --git a/t/t6200-fmt-merge-msg.sh b/t/t6200-fmt-merge-msg.sh
index b15582a..e4c2a6e 100755
--- a/t/t6200-fmt-merge-msg.sh
+++ b/t/t6200-fmt-merge-msg.sh
@@ -103,7 +103,7 @@
 	GNUPGHOME=. git fmt-merge-msg <.git/FETCH_HEAD >actual 2>&1 &&
 	grep "^Merge tag ${apos}signed-good-tag${apos}" actual &&
 	grep "^# gpg: Signature made" actual &&
-	grep "^# gpg: Can${apos}t check signature: \(public key not found\|No public key\)" actual
+	grep -E "^# gpg: Can${apos}t check signature: (public key not found|No public key)" actual
 '
 
 test_expect_success 'message for merging external branch' '