diff --git a/src/newgrf_generic.cpp b/src/newgrf_generic.cpp
--- a/src/newgrf_generic.cpp
+++ b/src/newgrf_generic.cpp
@@ -109,7 +109,7 @@ void ResetGenericCallbacks()
 void AddGenericCallback(uint8 feature, const GRFFile *file, const SpriteGroup *group)
 {
 	if (feature >= lengthof(_gcl)) {
-		GrfMsg(5, "AddGenericCallback: Unsupported feature {:#02X}", feature);
+		GrfMsg(5, "AddGenericCallback: Unsupported feature 0x{:02X}", feature);
 		return;
 	}