diff --git a/src/doomdef.h b/src/doomdef.h
index a9e18eaf6..c4896a764 100644
--- a/src/doomdef.h
+++ b/src/doomdef.h
@@ -146,6 +146,8 @@ extern FILE *logstream;
 #define VERSION    201 // Game version
 #define SUBVERSION 12  // more precise version number
 #define VERSIONSTRING "v2.1.12"
+// Hey! If you change this, add 1 to the MODVERSION below!
+// Otherwise we can't force updates!
 #endif
 
 // Modification options
@@ -201,7 +203,7 @@ extern FILE *logstream;
 // it's only for detection of the version the player is using so the MS can alert them of an update.
 // Only set it higher, not lower, obviously.
 // Note that we use this to help keep internal testing in check; this is why v2.1.0 is not version "1".
-#define MODVERSION 16
+#define MODVERSION 17