diff --git a/router/java/src/net/i2p/router/Blocklist.java b/router/java/src/net/i2p/router/Blocklist.java
index cbf3dbc6d..99247e0c2 100644
--- a/router/java/src/net/i2p/router/Blocklist.java
+++ b/router/java/src/net/i2p/router/Blocklist.java
@@ -147,7 +147,7 @@ public class Blocklist {
         _blocklistFeedFile = new File(BLOCKLIST_FEED_FILE);
         _haveIPv6 = TransportUtil.getIPv6Config(_context, "SSU") != TransportUtil.IPv6Config.IPV6_DISABLED &&
                     Addresses.isConnectedIPv6();
-        Blocklist = _haveIPv6 ? new LHMCache<BigInteger, Object>(MAX_IPV6_SINGLES) : null;
+        _singleIPv6Blocklist = _haveIPv6 ? new LHMCache<BigInteger, Object>(MAX_IPV6_SINGLES) : null;
     }
 
 
@@ -896,10 +896,12 @@ public class Blocklist {
      * @since IPv6
      */
     private boolean add(BigInteger ip) {
-        synchronized(_singleIPv6Blocklist) {
-            if (_singleIPv6Blocklist != null)
+        if (_singleIPv6Blocklist != null) {
+            synchronized(_singleIPv6Blocklist) {
                 return _singleIPv6Blocklist.put(ip, DUMMY) == null;
+            }
         }
+        return false;
     }
 
     /**
@@ -907,9 +909,10 @@ public class Blocklist {
      * @since 0.9.28
      */
     private void remove(BigInteger ip) {
-        synchronized(_singleIPv6Blocklist) {
-            if (_singleIPv6Blocklist != null)
+        if (_singleIPv6Blocklist != null) {
+            synchronized(_singleIPv6Blocklist) {
                 _singleIPv6Blocklist.remove(ip);
+            }
         }
     }
 
@@ -918,10 +921,12 @@ public class Blocklist {
      * @since IPv6
      */
     private boolean isOnSingleList(BigInteger ip) {
-        synchronized(_singleIPv6Blocklist) {
-            if (_singleIPv6Blocklist != null)
+        if (_singleIPv6Blocklist != null) {
+            synchronized(_singleIPv6Blocklist) {
                 return _singleIPv6Blocklist.get(ip) != null;
+            }
         }
+        return false;
     }
 
     /**
@@ -1365,10 +1370,12 @@ public class Blocklist {
     public List<BigInteger> getTransientIPv6Blocks() {
         if (!_haveIPv6)
             return Collections.<BigInteger>emptyList();
-        synchronized(_singleIPv6Blocklist) {
-            if (_singleIPv6Blocklist != null)
-                return new ArrayList<BigInteger>(_singleIPv6Blocklist.keySet());
+        if (_singleIPv6Blocklist != null) {
+            synchronized(_singleIPv6Blocklist) {
+                    return new ArrayList<BigInteger>(_singleIPv6Blocklist.keySet());
+            }
         }
+        return Collections.<BigInteger>emptyList();
     }
 
     /**