diff --git a/reactos/ntoskrnl/mm/ARM3/expool.c b/reactos/ntoskrnl/mm/ARM3/expool.c
index 4c5f46b0ccc..c10d8c87d56 100644
--- a/reactos/ntoskrnl/mm/ARM3/expool.c
+++ b/reactos/ntoskrnl/mm/ARM3/expool.c
@@ -520,7 +520,7 @@ ExFreePoolWithTag(IN PVOID P,
     // for this pool type
     //
     BlockSize = Entry->BlockSize;
-    PoolType = (Entry->PoolType & 3) - 1;
+    PoolType = (Entry->PoolType - 1) & BASE_POOL_TYPE_MASK;
     PoolDesc = PoolVector[PoolType];
 
     //