diff --git a/src/main/java/net/openhft/chronicle/hash/serialization/impl/ConstantSizeMarshaller.java b/src/main/java/net/openhft/chronicle/hash/serialization/impl/ConstantSizeMarshaller.java
index b42db841b..0ce1faf8e 100644
--- a/src/main/java/net/openhft/chronicle/hash/serialization/impl/ConstantSizeMarshaller.java
+++ b/src/main/java/net/openhft/chronicle/hash/serialization/impl/ConstantSizeMarshaller.java
@@ -59,6 +59,10 @@ public final class ConstantSizeMarshaller implements SizeMarshaller {
 
     @Override
     public void writeSize(Bytes out, long sizeToWrite) {
+        if (sizeToWrite != constantSize) {
+            throw new IllegalArgumentException(
+                    "sizeToWrite: " + sizeToWrite + ", constant size should be: " + constantSize);
+        }
         // do nothing
     }