diff --git a/evmjit/libevmjit/BasicBlock.h b/evmjit/libevmjit/BasicBlock.h
index 7a5364a4e..3591a6f54 100644
--- a/evmjit/libevmjit/BasicBlock.h
+++ b/evmjit/libevmjit/BasicBlock.h
@@ -57,7 +57,7 @@ public:
 	explicit BasicBlock(std::string _name, llvm::Function* _mainFunc, llvm::IRBuilder<>& _builder, bool isJumpDest);
 
 	BasicBlock(const BasicBlock&) = delete;
-	void operator=(const BasicBlock&) = delete;
+	BasicBlock& operator=(const BasicBlock&) = delete;
 
 	llvm::BasicBlock* llvm() { return m_llvmBB; }
 
diff --git a/evmjit/libevmjit/Runtime.h b/evmjit/libevmjit/Runtime.h
index 8cc5b7968..f97efa128 100644
--- a/evmjit/libevmjit/Runtime.h
+++ b/evmjit/libevmjit/Runtime.h
@@ -34,7 +34,7 @@ public:
 	Runtime(RuntimeData* _data, Env* _env);
 
 	Runtime(const Runtime&) = delete;
-	void operator=(const Runtime&) = delete;
+	Runtime& operator=(const Runtime&) = delete;
 
 	StackImpl& getStack() { return m_stack; }
 	MemoryImpl& getMemory() { return m_memory; }