diff --git a/src/BizHawk.Emulation.Cores/Waterbox/Heap.cs b/src/BizHawk.Emulation.Cores/Waterbox/Heap.cs
index 9ac0916276..bca60e01e8 100644
--- a/src/BizHawk.Emulation.Cores/Waterbox/Heap.cs
+++ b/src/BizHawk.Emulation.Cores/Waterbox/Heap.cs
@@ -73,7 +73,7 @@ namespace BizHawk.Emulation.Cores.Waterbox
 			if (!Sealed)
 			{
 				Memory.Protect(Memory.Start, Used, MemoryBlock.Protection.R);
-				_hash = WaterboxUtils.Hash(Memory.GetStream(Memory.Start, Used, false));
+				_hash = WaterboxUtils.Hash(Memory.GetStream(Memory.Start, WaterboxUtils.AlignUp(Used), false));
 				Sealed = true;
 			}
 			else