diff --git a/credential.c b/credential.c
index 9747f47b18bf2e..00ee4d62db121d 100644
--- a/credential.c
+++ b/credential.c
@@ -194,6 +194,8 @@ static void credential_write_item(FILE *fp, const char *key, const char *value)
 {
 	if (!value)
 		return;
+	if (strchr(value, '\n'))
+		die("credential value for %s contains newline", key);
 	fprintf(fp, "%s=%s\n", key, value);
 }
 
diff --git a/t/t0300-credentials.sh b/t/t0300-credentials.sh
index 03bd31e9f22a19..15cc3c5abb5b10 100755
--- a/t/t0300-credentials.sh
+++ b/t/t0300-credentials.sh
@@ -309,4 +309,10 @@ test_expect_success 'empty helper spec resets helper list' '
 	EOF
 '
 
+test_expect_success 'url parser rejects embedded newlines' '
+	test_must_fail git credential fill <<-\EOF
+	url=https://one.example.com?%0ahost=two.example.com/
+	EOF
+'
+
 test_done