diff --git a/projects/VC90/SimGear.vcproj b/projects/VC90/SimGear.vcproj
index 077af7ae..6c244843 100644
--- a/projects/VC90/SimGear.vcproj
+++ b/projects/VC90/SimGear.vcproj
@@ -1499,6 +1499,14 @@
 		<Filter
 			Name="Lib_sgstructure"
 			>
+			<File
+				RelativePath="..\..\simgear\structure\SGAtomic.hxx"
+				>
+			</File>
+			<File
+				RelativePath="..\..\simgear\structure\SGAtomic.cxx"
+				>
+			</File>
 			<File
 				RelativePath="..\..\simgear\structure\callback.hxx"
 				>