diff --git a/src/activitypub/index.js b/src/activitypub/index.js
index 4c1f3eee69..11f16322e2 100644
--- a/src/activitypub/index.js
+++ b/src/activitypub/index.js
@@ -585,6 +585,9 @@ ActivityPub.checkHeader = async (url, timeout) => {
 				.map(p => p.trim())
 				.reduce((memo, cur) => {
 					cur = cur.split('=');
+					if (cur.length < 2) {
+						cur.push('');
+					}
 					memo[cur[0]] = cur[1].slice(1, -1);
 					return memo;
 				}, {});