diff --git a/src/activitypub/helpers.js b/src/activitypub/helpers.js
index 9a6577af41..558a4ee8d7 100644
--- a/src/activitypub/helpers.js
+++ b/src/activitypub/helpers.js
@@ -66,8 +66,15 @@ Helpers.isUri = (value) => {
 };
 
 Helpers.assertAccept = (accept) => {
-	if (!accept) return false;
-	const normalized = accept.split(',').map(s => s.trim().replace(/\s*;\s*/g, ';')).join(',');
+	if (!accept) {
+		return false;
+	}
+
+	const normalized = accept
+		.split(',')
+		.map(s => s.trim().replace(/\s*;\s*/g, ';')) // spec allows spaces around semi-colon
+		.join(',');
+
 	return activitypub._constants.acceptableTypes.some(type => normalized.includes(type));
 };
 
diff --git a/src/middleware/activitypub.js b/src/middleware/activitypub.js
index 2805801561..9ea81c0035 100644
--- a/src/middleware/activitypub.js
+++ b/src/middleware/activitypub.js
@@ -19,11 +19,16 @@ middleware.pageview = async (req, res, next) => {
 middleware.assertS2S = async function (req, res, next) {
 	// For whatever reason, express accepts does not recognize "profile" as a valid differentiator
 	// Therefore, manual header parsing is used here.
-	const { accept, 'content-type': contentType } = req.headers;
+	let { accept, 'content-type': contentType } = req.headers;
 	if (!(accept || contentType)) {
 		return next('route');
 	}
 
+	// Normalize content-type
+	if (contentType) {
+		contentType = contentType.trim().replace(/\s*;\s*/g, ';'); // spec allows spaces around semi-colon
+	}
+
 	const pass = activitypub.helpers.assertAccept(accept) ||
 		(contentType && activitypub._constants.acceptableTypes.includes(contentType));