diff --git a/libraries/SE05X/src/SE05X.cpp b/libraries/SE05X/src/SE05X.cpp
index 1dff708e..2da7ea03 100644
--- a/libraries/SE05X/src/SE05X.cpp
+++ b/libraries/SE05X/src/SE05X.cpp
@@ -107,6 +107,11 @@ void SE05XClass::end()
     Se05x_API_SessionClose(&_se05x_session);
 }
 
+int SE05XClass::serialNumber(byte sn[])
+{
+    return serialNumber(sn, SE05X_SN_LENGTH);
+}
+
 int SE05XClass::serialNumber(byte sn[], size_t length)
 {
     size_t uidLen = length;
diff --git a/libraries/SE05X/src/SE05X.h b/libraries/SE05X/src/SE05X.h
index 38a459d8..124a82c7 100644
--- a/libraries/SE05X/src/SE05X.h
+++ b/libraries/SE05X/src/SE05X.h
@@ -44,6 +44,7 @@ class SE05XClass
     int begin();
     void end();
 
+    int serialNumber(byte sn[]);
     int serialNumber(byte sn[], size_t length);
 #if defined (ARDUINO)
     String serialNumber();