diff --git a/builtin/mailinfo.c b/builtin/mailinfo.c
index 71e6262a87..bfb32b7233 100644
--- a/builtin/mailinfo.c
+++ b/builtin/mailinfo.c
@@ -400,7 +400,7 @@ static int read_one_header_line(struct strbuf *line, FILE *in)
 			break;
 		if (strbuf_getline(&continuation, in, '\n'))
 			break;
-		continuation.buf[0] = '\n';
+		continuation.buf[0] = ' ';
 		strbuf_rtrim(&continuation);
 		strbuf_addbuf(line, &continuation);
 	}
diff --git a/t/t4152-am-subjects.sh b/t/t4152-am-subjects.sh
index 7222c06b80..37e5c0361c 100755
--- a/t/t4152-am-subjects.sh
+++ b/t/t4152-am-subjects.sh
@@ -58,7 +58,7 @@ test_expect_success 'long subject preserved (format-patch | am)' '
 test_expect_success 'long subject preserved (format-patch -k | am)' '
 	check_subject long-k
 '
-test_expect_failure 'long subject preserved (format-patch -k | am -k)' '
+test_expect_success 'long subject preserved (format-patch -k | am -k)' '
 	check_subject long-k -k
 '