diff --git a/projects/VC90/FlightGear/FlightGear.vcproj b/projects/VC90/FlightGear/FlightGear.vcproj
index 364454c1b..fd2548b0a 100644
--- a/projects/VC90/FlightGear/FlightGear.vcproj
+++ b/projects/VC90/FlightGear/FlightGear.vcproj
@@ -3198,6 +3198,30 @@
 				>
 			</File>
 		</Filter>
+		<Filter
+			Name="Lib_Radio"
+			>
+			<File
+				RelativePath="..\..\..\src\Radio\antenna.cxx"
+				>
+			</File>
+			<File
+				RelativePath="..\..\..\src\Radio\antenna.hxx"
+				>
+			</File>
+			<File
+				RelativePath="..\..\..\src\Radio\radio.cxx"
+				>
+			</File>
+			<File
+				RelativePath="..\..\..\src\Radio\radio.hxx"
+				>
+			</File>
+			<File
+				RelativePath="..\..\..\src\Radio\itm.cpp"
+				>
+			</File>
+		</Filter>
 		<Filter
 			Name="Lib_Scenery"
 			>
diff --git a/src/Radio/itm.cpp b/src/Radio/itm.cpp
index 1b970d067..184ac3765 100644
--- a/src/Radio/itm.cpp
+++ b/src/Radio/itm.cpp
@@ -1000,7 +1000,7 @@ double avar(double zzt, double zzl, double zzc, prop_type &prop, propv_type &pro
 			kdv = propv.mdvar;
 			no_situation_variability = kdv >= 20;
 			if (no_situation_variability)
-				no_situation_variability -= 20;
+				kdv -= 20;
 
 			no_location_variability = kdv >= 10;
 			if (no_location_variability)