diff --git a/utility/direct_pin_read.h b/utility/direct_pin_read.h
index 75660ac..d7d6b8c 100644
--- a/utility/direct_pin_read.h
+++ b/utility/direct_pin_read.h
@@ -3,6 +3,7 @@
 
 #if defined(__AVR__)
 
+#define IO_REG_TYPE                     uint8_t
 #define PIN_TO_BASEREG(pin)             (portInputRegister(digitalPinToPort(pin)))
 #define PIN_TO_BITMASK(pin)             (digitalPinToBitMask(pin))
 #define DIRECT_PIN_READ(base, mask)     (((*(base)) & (mask)) ? 1 : 0)