diff --git a/openttd.vcproj b/openttd.vcproj
--- a/openttd.vcproj
+++ b/openttd.vcproj
@@ -212,6 +212,9 @@
 				RelativePath=".\md5.c">
 			</File>
 			<File
+				RelativePath=".\mersenne.c">
+			</File>
+			<File
 				RelativePath="minilzo.c">
 				<FileConfiguration
 					Name="Release|Win32">