diff --git a/src/newgrf.cpp b/src/newgrf.cpp
index 29877b8dbe..b24ed48940 100644
--- a/src/newgrf.cpp
+++ b/src/newgrf.cpp
@@ -7797,7 +7797,7 @@ static bool ChangeGRFFeatureMaxVersion(size_t len, ByteReader *buf)
 	return true;
 }
 
-/** Callback function for 'FTST'->'SETP' to set the maximum version of the feature being tested. */
+/** Callback function for 'FTST'->'SETP' to set the bit number of global variable 9D (platform version) to set/unset the result of the feature test. */
 static bool ChangeGRFFeatureSetPlatformVarBit(size_t len, ByteReader *buf)
 {
 	if (len != 1) {