diff --git a/CardReader/ISO7816-reader.h b/CardReader/ISO7816-reader.h
index 5f556cb821f38dd02f8011099b86f839b327128c..4d5602e88bfbcb0cc5bd3323e86be6eb57ce0880 100644
--- a/CardReader/ISO7816-reader.h
+++ b/CardReader/ISO7816-reader.h
@@ -2,7 +2,8 @@
 #include "../common/ISO7816-common.h"
 #include <stdio.h>
 #include <util/delay.h>
-#define printf(...) 
+#define printf(...)
+#define printf_P(...)
 
 #define CARD_PRESENCE_REG_PORT PORTB
 #define CARD_PRESENCE_REG_PIN  PINB