diff --git a/commafeed-server/src/main/java/com/commafeed/backend/cache/CacheService.java b/commafeed-server/src/main/java/com/commafeed/backend/cache/CacheService.java
index f4065a97..dfa574f0 100644
--- a/commafeed-server/src/main/java/com/commafeed/backend/cache/CacheService.java
+++ b/commafeed-server/src/main/java/com/commafeed/backend/cache/CacheService.java
@@ -1,6 +1,7 @@
 package com.commafeed.backend.cache;
 
 import java.util.List;
+import java.util.Set;
 
 import org.apache.commons.codec.digest.DigestUtils;
 
@@ -14,7 +15,7 @@ import com.commafeed.frontend.model.UnreadCount;
 public abstract class CacheService {
 
 	// feed entries for faster refresh
-	public abstract List<String> getLastEntries(Feed feed);
+	public abstract Set<String> getLastEntries(Feed feed);
 
 	public abstract void setLastEntries(Feed feed, List<String> entries);
 
diff --git a/commafeed-server/src/main/java/com/commafeed/backend/cache/NoopCacheService.java b/commafeed-server/src/main/java/com/commafeed/backend/cache/NoopCacheService.java
index 4741f5ec..4b6ed9a0 100644
--- a/commafeed-server/src/main/java/com/commafeed/backend/cache/NoopCacheService.java
+++ b/commafeed-server/src/main/java/com/commafeed/backend/cache/NoopCacheService.java
@@ -2,6 +2,7 @@ package com.commafeed.backend.cache;
 
 import java.util.Collections;
 import java.util.List;
+import java.util.Set;
 
 import com.commafeed.backend.model.Feed;
 import com.commafeed.backend.model.FeedSubscription;
@@ -12,8 +13,8 @@ import com.commafeed.frontend.model.UnreadCount;
 public class NoopCacheService extends CacheService {
 
 	@Override
-	public List<String> getLastEntries(Feed feed) {
-		return Collections.emptyList();
+	public Set<String> getLastEntries(Feed feed) {
+		return Collections.emptySet();
 	}
 
 	@Override
diff --git a/commafeed-server/src/main/java/com/commafeed/backend/cache/RedisCacheService.java b/commafeed-server/src/main/java/com/commafeed/backend/cache/RedisCacheService.java
index 52ec76b5..4dc94f36 100644
--- a/commafeed-server/src/main/java/com/commafeed/backend/cache/RedisCacheService.java
+++ b/commafeed-server/src/main/java/com/commafeed/backend/cache/RedisCacheService.java
@@ -1,6 +1,5 @@
 package com.commafeed.backend.cache;
 
-import java.util.ArrayList;
 import java.util.List;
 import java.util.Set;
 import java.util.concurrent.TimeUnit;
@@ -29,14 +28,11 @@ public class RedisCacheService extends CacheService {
 	private final JedisPool pool;
 
 	@Override
-	public List<String> getLastEntries(Feed feed) {
-		List<String> list = new ArrayList<>();
+	public Set<String> getLastEntries(Feed feed) {
 		try (Jedis jedis = pool.getResource()) {
 			String key = buildRedisEntryKey(feed);
-			Set<String> members = jedis.smembers(key);
-			list.addAll(members);
+			return jedis.smembers(key);
 		}
-		return list;
 	}
 
 	@Override
diff --git a/commafeed-server/src/main/java/com/commafeed/backend/feed/FeedRefreshUpdater.java b/commafeed-server/src/main/java/com/commafeed/backend/feed/FeedRefreshUpdater.java
index 5e5a921d..9ee4b5f8 100644
--- a/commafeed-server/src/main/java/com/commafeed/backend/feed/FeedRefreshUpdater.java
+++ b/commafeed-server/src/main/java/com/commafeed/backend/feed/FeedRefreshUpdater.java
@@ -5,6 +5,7 @@ import java.util.Arrays;
 import java.util.Date;
 import java.util.Iterator;
 import java.util.List;
+import java.util.Set;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.locks.Lock;
 
@@ -121,7 +122,7 @@ public class FeedRefreshUpdater implements Managed {
 		boolean insertedAtLeastOneEntry = false;
 
 		if (!entries.isEmpty()) {
-			List<String> lastEntries = cache.getLastEntries(feed);
+			Set<String> lastEntries = cache.getLastEntries(feed);
 			List<String> currentEntries = new ArrayList<>();
 
 			List<FeedSubscription> subscriptions = null;