diff --git a/src/deh_tables.c b/src/deh_tables.c
index a96adf8ae..9fd00e0c3 100644
--- a/src/deh_tables.c
+++ b/src/deh_tables.c
@@ -4384,6 +4384,7 @@ const char *const MOBJFLAG_LIST[] = {
 	"NOCLIPTHING",
 	"GRENADEBOUNCE",
 	"RUNSPAWNFUNC",
+	"NOSTEPUP",
 	NULL
 };
 
diff --git a/src/info.c b/src/info.c
index 3998eb88d..20d6b8338 100644
--- a/src/info.c
+++ b/src/info.c
@@ -4469,7 +4469,7 @@ mobjinfo_t mobjinfo[NUMMOBJTYPES] =
 		100,            // mass
 		0,              // damage
 		sfx_None,       // activesound
-		MF_ENEMY|MF_SPECIAL|MF_NOGRAVITY|MF_SHOOTABLE, // flags
+		MF_ENEMY|MF_SPECIAL|MF_NOGRAVITY|MF_SHOOTABLE|MF_NOSTEPUP, // flags
 		(statenum_t)MT_MINE// raisestate
 	},
 
diff --git a/src/p_map.c b/src/p_map.c
index 337344b2f..81e5aeec5 100644
--- a/src/p_map.c
+++ b/src/p_map.c
@@ -2748,7 +2748,7 @@ increment_move
 					maxstep = 0;
 			}
 
-			if (thing->type == MT_SKIM)
+			if (thing->flags & MF_NOSTEPUP)
 				maxstep = 0;
 
 			if (tmceilingz - tmfloorz < thing->height
diff --git a/src/p_mobj.c b/src/p_mobj.c
index 259bf19d4..9d8b18f65 100644
--- a/src/p_mobj.c
+++ b/src/p_mobj.c
@@ -10486,10 +10486,13 @@ void P_SceneryThinker(mobj_t *mobj)
 		P_CheckPosition(mobj, mobj->x, mobj->y); // Need this to pick up objects!
 		if (P_MobjWasRemoved(mobj))
 			return;
-		mobj->floorz = tmfloorz;
-		mobj->ceilingz = tmceilingz;
-		mobj->floorrover = tmfloorrover;
-		mobj->ceilingrover = tmceilingrover;
+		if (!(mobj->flags & MF_NOSTEPUP))
+		{
+			mobj->floorz = tmfloorz;
+			mobj->ceilingz = tmceilingz;
+			mobj->floorrover = tmfloorrover;
+			mobj->ceilingrover = tmceilingrover;
+		}
 	}
 	else
 	{
diff --git a/src/p_mobj.h b/src/p_mobj.h
index 4a8427669..7864ec563 100644
--- a/src/p_mobj.h
+++ b/src/p_mobj.h
@@ -87,7 +87,7 @@
 // block or has the MF_NOBLOCKMAP flag set.
 // Links should only be modified by the P_[Un]SetThingPosition()
 // functions.
-// Do not change the MF_NO? flags while a thing is valid.
+// Do not change the MF_NO? flags while a thing is valid with the exception of the MF_NOSTEPUP flag.
 //
 // Any questions?
 //
@@ -159,7 +159,9 @@ typedef enum
 	MF_GRENADEBOUNCE    = 1<<28,
 	// Run the action thinker on spawn.
 	MF_RUNSPAWNFUNC     = 1<<29,
-	// free: 1<<30 and 1<<31
+	// Don't allow the mobj to be affected by the stepup code.
+	MF_NOSTEPUP         = 1<<30,
+	// free: to and including 1<<31
 } mobjflag_t;
 
 typedef enum