diff --git a/openttd.vcproj b/openttd.vcproj
index f1b0779797..1c43864bc5 100644
--- a/openttd.vcproj
+++ b/openttd.vcproj
@@ -211,6 +211,9 @@
 			<File
 				RelativePath=".\md5.c">
 			</File>
+			<File
+				RelativePath=".\mersenne.c">
+			</File>
 			<File
 				RelativePath="minilzo.c">
 				<FileConfiguration