diff --git a/src/wifi/model/wifi-default-ack-manager.cc b/src/wifi/model/wifi-default-ack-manager.cc
index 673e9cd23..ca286330b 100644
--- a/src/wifi/model/wifi-default-ack-manager.cc
+++ b/src/wifi/model/wifi-default-ack-manager.cc
@@ -699,7 +699,7 @@ WifiDefaultAckManager::TryUlMuTransmission(Ptr<const WifiMpdu> mpdu,
         {
             uint16_t aid12 = userInfo.GetAid12();
 
-            if (aid12 == 2046)
+            if (aid12 == NO_USER_STA_ID)
             {
                 NS_LOG_INFO("Unallocated RU");
                 continue;
diff --git a/src/wifi/model/wifi-tx-vector.h b/src/wifi/model/wifi-tx-vector.h
index 8a81c3821..7f298b927 100644
--- a/src/wifi/model/wifi-tx-vector.h
+++ b/src/wifi/model/wifi-tx-vector.h
@@ -33,6 +33,9 @@
 namespace ns3
 {
 
+/// STA_ID for a RU that is intended for no user (Section 26.11.1 802.11ax-2021)
+static constexpr uint16_t NO_USER_STA_ID = 2046;
+
 /// HE MU specific user transmission parameters.
 struct HeMuUserInfo
 {