diff --git a/libs/JSystem/include/JSystem/JKernel/JKRExpHeap.h b/libs/JSystem/include/JSystem/JKernel/JKRExpHeap.h
index 1535ba757b..cf6bb819eb 100644
--- a/libs/JSystem/include/JSystem/JKernel/JKRExpHeap.h
+++ b/libs/JSystem/include/JSystem/JKernel/JKRExpHeap.h
@@ -35,7 +35,7 @@ public:
         CMemBlock* getNextBlock() const { return mNext; }
         u32 getSize() const { return size; }
         u8 getGroupId() const { return mGroupId; }
-        static CMemBlock* getBlock(void* data) { return (CMemBlock*)((uintptr_t)data + -0x10); }
+        static CMemBlock* getBlock(void* data) { return (CMemBlock*)((uintptr_t)data + -sizeof(CMemBlock)); }
 
     private:
         /* 0x0 */ u16 mMagic;
diff --git a/libs/JSystem/src/JKernel/JKRExpHeap.cpp b/libs/JSystem/src/JKernel/JKRExpHeap.cpp
index 1c6d16c1a9..1f570dd421 100644
--- a/libs/JSystem/src/JKernel/JKRExpHeap.cpp
+++ b/libs/JSystem/src/JKernel/JKRExpHeap.cpp
@@ -464,7 +464,7 @@ void JKRExpHeap::do_freeAll() {
     JKRHeap::callAllDisposer();
     mHeadFreeList = (CMemBlock*)mStart;
     mTailFreeList = mHeadFreeList;
-    mHeadFreeList->initiate(NULL, NULL, mSize - 0x10, 0, 0);
+    mHeadFreeList->initiate(NULL, NULL, mSize - sizeof(CMemBlock), 0, 0);
     mHeadUsedList = NULL;
     mTailUsedList = NULL;
 #if DEBUG