diff --git a/src/WebOTA.cpp b/src/WebOTA.cpp
index 4e4df63..8d97712 100644
--- a/src/WebOTA.cpp
+++ b/src/WebOTA.cpp
@@ -235,7 +235,7 @@ String get_mac_address() {
 
 	// Build a string and return it
 	char buf[20] = "";
-	snprintf(buf, sizeof(buf), "%X:%X:%X:%X:%X:%X", mac[0],mac[1],mac[2],mac[3],mac[4],mac[5]);
+	snprintf(buf, sizeof(buf), "%02X:%02X:%02X:%02X:%02X:%02X", mac[0],mac[1],mac[2],mac[3],mac[4],mac[5]);
 
 	String ret = buf;