diff --git a/cores/esp8266/Arduino.h b/cores/esp8266/Arduino.h
index cc3525015..66e2eeca5 100644
--- a/cores/esp8266/Arduino.h
+++ b/cores/esp8266/Arduino.h
@@ -178,7 +178,7 @@ void ets_intr_unlock();
 #define _NOP() do { __asm__ volatile ("nop"); } while (0)
 #endif
 
-typedef unsigned int word;
+typedef uint16_t word;
 
 #define bit(b) (1UL << (b))
 #define _BV(b) (1UL << (b))