diff --git a/cores/arduino/board.cpp b/cores/arduino/board.cpp
index a8b8703..4b06378 100644
--- a/cores/arduino/board.cpp
+++ b/cores/arduino/board.cpp
@@ -8,7 +8,7 @@
 void pre_init(void)
 {
     // set irq vector to ram region
-    write_csr(mtvec, 0x020000c0);
+    write_csr(mtvec, 0x02000000);
 
     HAL_Init();
 
@@ -35,8 +35,10 @@ void post_init(void)
 // print text if Serial is enabled
 extern "C" void ErrorMsgHandler(const char * msg)
 {
+#ifdef HardwareSerial_h
     if(Serial)
         Serial.println(msg);
+#endif
 }