diff --git a/src/main/java/net/openhft/chronicle/map/ReplicatedChronicleMap.java b/src/main/java/net/openhft/chronicle/map/ReplicatedChronicleMap.java
index 8247922f2..354b094b1 100644
--- a/src/main/java/net/openhft/chronicle/map/ReplicatedChronicleMap.java
+++ b/src/main/java/net/openhft/chronicle/map/ReplicatedChronicleMap.java
@@ -488,6 +488,9 @@ final class ReplicatedChronicleMap<K, KI, MKI extends MetaBytesInterop<K, ? supe
                         final NativeBytes k = wrap(entry.address() + keyPosition, keySize);
                         final NativeBytes v = wrap(entry.address() + valuePosition, valueSize);
 
+                        assert k.remaining() > 0 : "keySize:" + keySize;
+                        assert v.remaining() > 0 : "valueSize:" + valueSize;
+
                         return callback.onEntry(k, v,
                                 timestamp,
                                 identifier,
diff --git a/src/main/java/net/openhft/chronicle/map/VanillaChronicleMap.java b/src/main/java/net/openhft/chronicle/map/VanillaChronicleMap.java
index 70cf8a074..ed1ec7a14 100755
--- a/src/main/java/net/openhft/chronicle/map/VanillaChronicleMap.java
+++ b/src/main/java/net/openhft/chronicle/map/VanillaChronicleMap.java
@@ -1865,7 +1865,7 @@ class VanillaChronicleMap<K, KI, MKI extends MetaBytesInterop<K, ? super KI>,
                 boolean success = false;
 
                 try {
-                    success = segmentHeader.tryRWWriteLock(LOCK_OFFSET, lockTimeOutNS);
+                    success = segmentHeader.tryRWReadLock(LOCK_OFFSET, lockTimeOutNS);
                 } catch (InterruptedException e) {
                     Thread.currentThread().interrupt();
                 }
@@ -1944,7 +1944,7 @@ class VanillaChronicleMap<K, KI, MKI extends MetaBytesInterop<K, ? super KI>,
         public final void readUnlock() {
             try {
 //                segmentHeader.unlockRWReadLock(LOCK_OFFSET);
-                segmentHeader.unlockRWWriteLock(LOCK_OFFSET);
+                segmentHeader.unlockRWReadLock(LOCK_OFFSET);
 //                lock.readLock().unlock();
             } catch (IllegalMonitorStateException e) {
                 errorListener.errorOnUnlock(e);