diff --git a/libraries/WiFiS3/src/WiFi.cpp b/libraries/WiFiS3/src/WiFi.cpp
index f99fd6db..6cd63526 100644
--- a/libraries/WiFiS3/src/WiFi.cpp
+++ b/libraries/WiFiS3/src/WiFi.cpp
@@ -219,7 +219,7 @@ static bool macStr2macArray(uint8_t *mac_out, const char *mac_in) {
       return false;
    }
 
-   for(int i = 0; i < 6; i++) {
+   for(int i = 0; i < WL_MAC_ADDR_LENGTH; i++) {
       std::string str_num(mac_in+(i*3),2);
       *(mac_out+i) = std::stoul(str_num,nullptr,16);
    }
diff --git a/libraries/WiFiS3/src/WiFi.h b/libraries/WiFiS3/src/WiFi.h
index 68774fb0..8a50f417 100644
--- a/libraries/WiFiS3/src/WiFi.h
+++ b/libraries/WiFiS3/src/WiFi.h
@@ -19,6 +19,7 @@
 
 
 #define WIFI_FIRMWARE_LATEST_VERSION "0.4.1"
+#define WL_MAC_ADDR_LENGTH 6
 
 class CAccessPoint {
    public: