diff --git a/src/SysYIRGenerator.cpp b/src/SysYIRGenerator.cpp
index 1fb7305..2fa2be8 100644
--- a/src/SysYIRGenerator.cpp
+++ b/src/SysYIRGenerator.cpp
@@ -712,7 +712,7 @@ std::any SysYIRGenerator::visitReturnStmt(SysYParser::ReturnStmtContext *ctx) {
   }
 
   Type* funcType = builder.getBasicBlock()->getParent()->getReturnType();
-    if (funcType!= returnValue->getType() && returnValue != nullptr) {
+    if (returnValue != nullptr && funcType!= returnValue->getType()) {
       ConstantValue * constValue = dynamic_cast<ConstantValue *>(returnValue);
       if (constValue != nullptr) {
         if (funcType == Type::getFloatType()) {