diff --git a/demo/dio.c b/demo/dio.c
index 16464b2..d7b5227 100644
--- a/demo/dio.c
+++ b/demo/dio.c
@@ -58,6 +58,10 @@ int main(int argc, char *argv[])
 		printf("for input.\n");
 		ret = comedi_dio_config(device, options.subdevice, options.channel, COMEDI_INPUT);
 	}
+	if(ret < 0){
+		comedi_perror("comedi_dio_config");
+		exit(-1);
+	}
 	return 0;
 }