diff --git a/src/remote/activitypub/resolver.ts b/src/remote/activitypub/resolver.ts
index bff84f5781..049e645e47 100644
--- a/src/remote/activitypub/resolver.ts
+++ b/src/remote/activitypub/resolver.ts
@@ -19,16 +19,20 @@ export default class Resolver {
 			: value;
 
 		switch (collection.type) {
-		case 'Collection':
-			collection.objects = collection.items;
-			break;
+			case 'Collection': {
+				collection.objects = collection.items;
+				break;
+			}
 
-		case 'OrderedCollection':
-			collection.objects = collection.orderedItems;
-			break;
+			case 'OrderedCollection': {
+				collection.objects = collection.orderedItems;
+				break;
+			}
 
-		default:
-			throw new Error(`unknown collection type: ${collection.type}`);
+			default: {
+				logger.error(`unknown collection type: ${collection.type}`);
+				throw new Error(`unknown collection type: ${collection.type}`);
+			}
 		}
 
 		return collection;
@@ -36,6 +40,7 @@ export default class Resolver {
 
 	public async resolve(value: any): Promise<IObject> {
 		if (value == null) {
+			logger.error('resolvee is null (or undefined)');
 			throw new Error('resolvee is null (or undefined)');
 		}
 
@@ -44,6 +49,7 @@ export default class Resolver {
 		}
 
 		if (this.history.has(value)) {
+			logger.error(`cannot resolve already resolved one`);
 			throw new Error('cannot resolve already resolved one');
 		}
 
@@ -59,6 +65,7 @@ export default class Resolver {
 			},
 			json: true
 		}).catch(e => {
+			logger.error(`request error: ${e.message}`);
 			throw new Error(`request error: ${e.message}`);
 		});