diff --git a/combine-diff.c b/combine-diff.c
index 24ca7e2334..fd6d63c703 100644
--- a/combine-diff.c
+++ b/combine-diff.c
@@ -1339,7 +1339,8 @@ void diff_tree_combined(const unsigned char *sha1,
 		if (show_log_first && i == 0) {
 			show_log(rev);
 
-			if (rev->verbose_header && opt->output_format)
+			if (rev->verbose_header && opt->output_format &&
+			    opt->output_format != DIFF_FORMAT_NO_OUTPUT)
 				printf("%s%c", diff_line_prefix(opt),
 				       opt->line_termination);
 		}
diff --git a/t/t1507-rev-parse-upstream.sh b/t/t1507-rev-parse-upstream.sh
index 178694ee63..1978947c41 100755
--- a/t/t1507-rev-parse-upstream.sh
+++ b/t/t1507-rev-parse-upstream.sh
@@ -121,7 +121,7 @@ test_expect_success 'merge my-side@{u} records the correct name' '
 	git branch -D new ;# can fail but is ok
 	git branch -t new my-side@{u} &&
 	git merge -s ours new@{u} &&
-	git show -s --pretty=format:%s >actual &&
+	git show -s --pretty=tformat:%s >actual &&
 	echo "Merge remote-tracking branch ${sq}origin/side${sq}" >expect &&
 	test_cmp expect actual
 )
diff --git a/t/t7007-show.sh b/t/t7007-show.sh
index e41fa00b80..1b824fe5ed 100755
--- a/t/t7007-show.sh
+++ b/t/t7007-show.sh
@@ -24,7 +24,8 @@ test_expect_success 'set up a bit of history' '
 	git tag -m "annotated tag" annotated &&
 	git checkout -b side HEAD^^ &&
 	test_commit side2 &&
-	test_commit side3
+	test_commit side3 &&
+	test_merge merge main3
 '
 
 test_expect_success 'showing two commits' '
@@ -109,8 +110,11 @@ test_expect_success 'showing range' '
 '
 
 test_expect_success '-s suppresses diff' '
-	echo main3 >expect &&
-	git show -s --format=%s main3 >actual &&
+	cat >expect <<-\EOF &&
+	merge
+	main3
+	EOF
+	git show -s --format=%s merge main3 >actual &&
 	test_cmp expect actual
 '
 
diff --git a/t/t7600-merge.sh b/t/t7600-merge.sh
index 10aa028017..b16462132f 100755
--- a/t/t7600-merge.sh
+++ b/t/t7600-merge.sh
@@ -57,11 +57,10 @@ create_merge_msgs () {
 		git log --no-merges ^HEAD c2 c3
 	} >squash.1-5-9 &&
 	: >msg.nologff &&
-	echo >msg.nolognoff &&
+	: >msg.nolognoff &&
 	{
 		echo "* tag 'c3':" &&
-		echo "  commit 3" &&
-		echo
+		echo "  commit 3"
 	} >msg.log
 }
 
@@ -71,7 +70,7 @@ verify_merge () {
 	git diff --exit-code &&
 	if test -n "$3"
 	then
-		git show -s --pretty=format:%s HEAD >msg.act &&
+		git show -s --pretty=tformat:%s HEAD >msg.act &&
 		test_cmp "$3" msg.act
 	fi
 }
@@ -620,10 +619,10 @@ test_expect_success 'merge early part of c2' '
 	git tag c6 &&
 	git branch -f c5-branch c5 &&
 	git merge c5-branch~1 &&
-	git show -s --pretty=format:%s HEAD >actual.branch &&
+	git show -s --pretty=tformat:%s HEAD >actual.branch &&
 	git reset --keep HEAD^ &&
 	git merge c5~1 &&
-	git show -s --pretty=format:%s HEAD >actual.tag &&
+	git show -s --pretty=tformat:%s HEAD >actual.tag &&
 	test_cmp expected.branch actual.branch &&
 	test_cmp expected.tag actual.tag
 '