diff --git a/Marlin/fastio.h b/Marlin/fastio.h
index bbceaa6a33..0f7df9765c 100644
--- a/Marlin/fastio.h
+++ b/Marlin/fastio.h
@@ -31,7 +31,7 @@
 
 #include <stdint.h>
 
-typedef uint8_t pin_t;
+typedef int8_t pin_t;
 
 #include <avr/io.h>