diff --git a/libraries/Crypto/BigNumberUtil.h b/libraries/Crypto/BigNumberUtil.h
index 28d83e7f..2212cbb1 100644
--- a/libraries/Crypto/BigNumberUtil.h
+++ b/libraries/Crypto/BigNumberUtil.h
@@ -27,8 +27,9 @@
 #include <stddef.h>
 
 // Define exactly one of these to 1 to set the size of the basic limb type.
-#if defined(__AVR__)
+#if defined(__AVR__) || defined(ESP8266)
 // 16-bit limbs seem to give the best performance on 8-bit AVR micros.
+// They also seem to give better performance on ESP8266 as well.
 #define BIGNUMBER_LIMB_8BIT  0
 #define BIGNUMBER_LIMB_16BIT 1
 #define BIGNUMBER_LIMB_32BIT 0