diff --git a/command/rakp12.hpp b/command/rakp12.hpp
index fb9a499..189b5e5 100644
--- a/command/rakp12.hpp
+++ b/command/rakp12.hpp
@@ -8,6 +8,8 @@
 namespace command
 {
 
+constexpr size_t userNameMaxLen = 16;
+
 /**
  * @struct RAKP1request
  *
@@ -23,7 +25,7 @@
     uint8_t req_max_privilege_level;
     uint16_t reserved3;
     uint8_t user_name_len;
-    char user_name[16];
+    char user_name[userNameMaxLen];
 } __attribute__((packed));
 
 /**