diff --git a/cores/arduino/UARTClass.cpp b/cores/arduino/UARTClass.cpp
index 6092fc9..9768a46 100644
--- a/cores/arduino/UARTClass.cpp
+++ b/cores/arduino/UARTClass.cpp
@@ -107,7 +107,7 @@ UARTClass::read(void)
   while(this->_buff->available()){
     return this->_buff->read_char();
   }
-  return 0;
+  return -1;
 }
 
 void