diff --git a/src/main/java/org/ultramine/server/chunk/OffHeapChunkStorage.java b/src/main/java/org/ultramine/server/chunk/OffHeapChunkStorage.java
index 93a811f..9b7323a 100644
--- a/src/main/java/org/ultramine/server/chunk/OffHeapChunkStorage.java
+++ b/src/main/java/org/ultramine/server/chunk/OffHeapChunkStorage.java
@@ -61,7 +61,7 @@
 	
 	public long getUsedMemory()
 	{
-		return (counter+1-freeSlots.size())*SLOT_SIZE;
+		return ((long)counter+1-freeSlots.size())*SLOT_SIZE;
 	}
 	
 	private static class MemChunk