diff --git a/src/p_mobj.h b/src/p_mobj.h
index ec25855d8..f6ebd3cad 100644
--- a/src/p_mobj.h
+++ b/src/p_mobj.h
@@ -194,6 +194,7 @@ typedef enum
 	MF2_AMBUSH         = 1<<27, // Alternate behaviour typically set by MTF_AMBUSH
 	MF2_LINKDRAW       = 1<<28, // Draw vissprite of mobj immediately before/after tracer's vissprite (dependent on dispoffset and position)
 	MF2_SHIELD         = 1<<29, // Thinker calls P_AddShield/P_ShieldLook (must be partnered with MF_SCENERY to use)
+	// free: to and including 1<<31
 } mobjflag2_t;
 
 typedef enum