diff --git a/t/t5573-pull-verify-signatures.sh b/t/t5573-pull-verify-signatures.sh
index 9594e891f4..747775c147 100755
--- a/t/t5573-pull-verify-signatures.sh
+++ b/t/t5573-pull-verify-signatures.sh
@@ -29,7 +29,7 @@ test_expect_success GPG 'create repositories with signed commits' '
 		echo 4 >d && git add d &&
 		test_tick && git commit -S -m "bad" &&
 		git cat-file commit HEAD >raw &&
-		sed -e "s/bad/forged bad/" raw >forged &&
+		sed -e "s/^bad/forged bad/" raw >forged &&
 		git hash-object -w -t commit forged >forged.commit &&
 		git checkout $(cat forged.commit)
 	) &&
diff --git a/t/t7030-verify-tag.sh b/t/t7030-verify-tag.sh
index b4b49eeb08..291a1e2b07 100755
--- a/t/t7030-verify-tag.sh
+++ b/t/t7030-verify-tag.sh
@@ -74,7 +74,7 @@ test_expect_success GPG 'verify and show signatures' '
 
 test_expect_success GPG 'detect fudged signature' '
 	git cat-file tag seventh-signed >raw &&
-	sed -e "s/seventh/7th forged/" raw >forged1 &&
+	sed -e "/^tag / s/seventh/7th forged/" raw >forged1 &&
 	git hash-object -w -t tag forged1 >forged1.tag &&
 	test_must_fail git verify-tag $(cat forged1.tag) 2>actual1 &&
 	grep "BAD signature from" actual1 &&
diff --git a/t/t7510-signed-commit.sh b/t/t7510-signed-commit.sh
index 663bf68def..6e2015ed9a 100755
--- a/t/t7510-signed-commit.sh
+++ b/t/t7510-signed-commit.sh
@@ -142,8 +142,7 @@ test_expect_success GPG 'show signed commit with signature' '
 
 test_expect_success GPG 'detect fudged signature' '
 	git cat-file commit seventh-signed >raw &&
-
-	sed -e "s/seventh/7th forged/" raw >forged1 &&
+	sed -e "s/^seventh/7th forged/" raw >forged1 &&
 	git hash-object -w -t commit forged1 >forged1.commit &&
 	test_must_fail git verify-commit $(cat forged1.commit) &&
 	git show --pretty=short --show-signature $(cat forged1.commit) >actual1 &&
diff --git a/t/t7612-merge-verify-signatures.sh b/t/t7612-merge-verify-signatures.sh
index e797c74112..e2b1df817a 100755
--- a/t/t7612-merge-verify-signatures.sh
+++ b/t/t7612-merge-verify-signatures.sh
@@ -23,7 +23,7 @@ test_expect_success GPG 'create signed commits' '
 	echo 3 >bar && git add bar &&
 	test_tick && git commit -S -m "bad on side" &&
 	git cat-file commit side-bad >raw &&
-	sed -e "s/bad/forged bad/" raw >forged &&
+	sed -e "s/^bad/forged bad/" raw >forged &&
 	git hash-object -w -t commit forged >forged.commit &&
 	git checkout initial &&