diff --git a/src/flex/flex.cxx b/src/flex/flex.cxx
index fcf763a5..4e63362e 100644
--- a/src/flex/flex.cxx
+++ b/src/flex/flex.cxx
@@ -23,6 +23,8 @@
  */
 
 #include <iostream>
+#include <string>
+#include <stdexcept>
 
 #include "flex.h"
 
@@ -33,7 +35,8 @@ Flex::Flex(int pin)
 {
   if ( !(m_aio = mraa_aio_init(pin)) )
     {
-      cerr << __FUNCTION__ << ": mraa_aio_init() failed" << endl;
+      throw std::invalid_argument(std::string(__FUNCTION__) +
+                                  ": mraa_aio_init() failed, invalid pin?");
       return;
     }
 }