diff --git a/IDEHelper/Backend/BeIRCodeGen.cpp b/IDEHelper/Backend/BeIRCodeGen.cpp
index b417b7db..3190a2e8 100644
--- a/IDEHelper/Backend/BeIRCodeGen.cpp
+++ b/IDEHelper/Backend/BeIRCodeGen.cpp
@@ -874,6 +874,12 @@ void BeIRCodeGen::Read(BeValue*& beValue)
 			beValue = beConst;
 			return;
 		}
+		else if (constType == BfConstType_Undef)
+		{
+			CMD_PARAM(BeType*, type);
+			beValue = mBeModule->CreateUndefValue(type);
+			return;
+		}
 
 		bool isSigned = false;
 		BeType* llvmConstType = GetBeType(typeCode, isSigned);
diff --git a/IDEHelper/Compiler/BfIRBuilder.cpp b/IDEHelper/Compiler/BfIRBuilder.cpp
index 2429812b..ef688514 100644
--- a/IDEHelper/Compiler/BfIRBuilder.cpp
+++ b/IDEHelper/Compiler/BfIRBuilder.cpp
@@ -1950,6 +1950,12 @@ void BfIRBuilder::Write(const BfIRValue& irValue)
 				Write(constant->mInt64);
 			}
 			break;
+		case (int)BfConstType_Undef:
+			{	
+				auto undefConst = (BfConstantUndef*)constant;
+				Write(undefConst->mType);
+			}
+			break;
 		default:			
 			{
 				BF_FATAL("Unhandled");
diff --git a/IDEHelper/Compiler/BfIRCodeGen.cpp b/IDEHelper/Compiler/BfIRCodeGen.cpp
index 79ca27c1..7f0cb2f0 100644
--- a/IDEHelper/Compiler/BfIRCodeGen.cpp
+++ b/IDEHelper/Compiler/BfIRCodeGen.cpp
@@ -935,6 +935,12 @@ void BfIRCodeGen::Read(llvm::Value*& llvmValue, BfIRCodeGenEntry** codeGenEntry)
 						
 			return;
 		}
+		else if (constType == BfConstType_Undef)
+		{
+			CMD_PARAM(llvm::Type*, type);
+			llvmValue = llvm::UndefValue::get(type);
+			return;
+		}
 
 		bool isSigned;
 		llvm::Type* llvmConstType = GetLLVMType(typeCode, isSigned);