diff --git a/src/wifi/model/wifi-mode.cc b/src/wifi/model/wifi-mode.cc
index 83e42a8ad..92198bbcd 100644
--- a/src/wifi/model/wifi-mode.cc
+++ b/src/wifi/model/wifi-mode.cc
@@ -157,8 +157,7 @@ WifiMode::GetMcsValue() const
     }
     else
     {
-        // We should not go here!
-        NS_ASSERT(false);
+        NS_ASSERT_MSG(false, "GetMcsValue() cannot be called for non-HT modulations");
         return 0;
     }
 }
diff --git a/src/wifi/model/wifi-mode.h b/src/wifi/model/wifi-mode.h
index c8f33c43e..833be85d4 100644
--- a/src/wifi/model/wifi-mode.h
+++ b/src/wifi/model/wifi-mode.h
@@ -113,6 +113,9 @@ class WifiMode
     uint16_t GetConstellationSize() const;
     /**
      * @returns the MCS value.
+     *
+     * This method cannot be called for non-HT modulations, because Modulation and Coding Scheme
+     * (MCS) is a concept introduced by the 802.11n amendment.
      */
     uint8_t GetMcsValue() const;
     /**