diff --git a/include/gfx/bitmap.c b/include/gfx/bitmap.c
index 07f7166..516db92 100644
--- a/include/gfx/bitmap.c
+++ b/include/gfx/bitmap.c
@@ -1164,8 +1164,8 @@ void bmu_bitblit(const Bitmap * dbm, int dx, int dy, const Bitmap * sbm, int sx,
 
 	if (op & BLIT_SRC)
 	{
-		if (!pattern)
-			pattern = sp;
+		if (!pat)
+			pat = sp;
 
 		if (reverse)
 		{
diff --git a/oscar64/Errors.h b/oscar64/Errors.h
index f824e15..24d9f73 100644
--- a/oscar64/Errors.h
+++ b/oscar64/Errors.h
@@ -27,6 +27,7 @@ enum ErrorID
 	EWARN_USE_OF_UNINITIALIZED_VARIABLE,
 	EWARN_MISSING_RETURN_STATEMENT,
 	EWARN_UNREACHABLE_CODE,
+	EWARN_NULL_POINTER_DEREFERENCED,
 
 	EERR_GENERIC = 3000,
 	EERR_FILE_NOT_FOUND,
diff --git a/oscar64/NativeCodeGenerator.cpp b/oscar64/NativeCodeGenerator.cpp
index 79c3608..1999929 100644
--- a/oscar64/NativeCodeGenerator.cpp
+++ b/oscar64/NativeCodeGenerator.cpp
@@ -4541,7 +4541,8 @@ void NativeCodeInstruction::Assemble(NativeCodeBasicBlock* block)
 			}
 			else
 			{
-				assert(mAddress != 0);
+				if (mAddress == 0)
+					block->mProc->mGenerator->mErrors->Error(mIns->mLocation, EWARN_NULL_POINTER_DEREFERENCED, "nullptr dereferenced");
 				block->PutByte(uint8(mAddress));
 			}
 			break;
@@ -4608,6 +4609,8 @@ void NativeCodeInstruction::Assemble(NativeCodeBasicBlock* block)
 			}
 			else
 			{
+				if (mAddress == 0)
+					block->mProc->mGenerator->mErrors->Error(mIns->mLocation, EWARN_NULL_POINTER_DEREFERENCED, "nullptr dereferenced");
 				block->PutWord(uint16(mAddress));
 			}
 			break;
@@ -39601,8 +39604,9 @@ void NativeCodeBasicBlock::CopyCode(NativeCodeProcedure * proc, uint8* target)
 	}
 }
 
-NativeCodeBasicBlock::NativeCodeBasicBlock(void)
+NativeCodeBasicBlock::NativeCodeBasicBlock(NativeCodeProcedure* proc)
 {
+	mProc = proc;
 	mBranch = ASMIT_RTS;
 	mBranchIns = nullptr;
 	mTrueJump = mFalseJump = NULL;
@@ -41209,7 +41213,7 @@ void NativeCodeProcedure::BuildDataFlowSets(void)
 
 NativeCodeBasicBlock* NativeCodeProcedure::AllocateBlock(void)
 {
-	NativeCodeBasicBlock* block = new NativeCodeBasicBlock();
+	NativeCodeBasicBlock* block = new NativeCodeBasicBlock(this);
 	block->mNoFrame = mNoFrame;
 	block->mFrameOffset = mFrameOffset;
 	block->mIndex = mTempBlocks++;
@@ -41223,7 +41227,7 @@ NativeCodeBasicBlock* NativeCodeProcedure::CompileBlock(InterCodeProcedure* ipro
 	if (tblocks[sblock->mIndex])
 		return tblocks[sblock->mIndex];
 
-	NativeCodeBasicBlock* block = new NativeCodeBasicBlock();
+	NativeCodeBasicBlock* block = new NativeCodeBasicBlock(this);
 	block->mNoFrame = mNoFrame;
 	block->mFrameOffset = mFrameOffset;
 	mBlocks.Push(block);
diff --git a/oscar64/NativeCodeGenerator.h b/oscar64/NativeCodeGenerator.h
index 397bd28..9cb807a 100644
--- a/oscar64/NativeCodeGenerator.h
+++ b/oscar64/NativeCodeGenerator.h
@@ -210,9 +210,10 @@ public:
 class NativeCodeBasicBlock
 {
 public:
-	NativeCodeBasicBlock(void);
+	NativeCodeBasicBlock(NativeCodeProcedure * proc);
 	~NativeCodeBasicBlock(void);
 
+	NativeCodeProcedure				*	mProc;
 	ExpandingArray<uint8>				mCode;
 	ExpandingArray<CodeLocation>		mCodeLocations;