diff --git a/src/lua_baselib.c b/src/lua_baselib.c
index 00a51927..e8e8fd02 100644
--- a/src/lua_baselib.c
+++ b/src/lua_baselib.c
@@ -560,15 +560,12 @@ static int lib_pCheckSolidLava(lua_State *L)
 {
 	mobj_t *mo = *((mobj_t **)luaL_checkudata(L, 1, META_MOBJ));
 	ffloor_t *rover = *((ffloor_t **)luaL_checkudata(L, 2, META_FFLOOR));
-	sector_t *bound = *((sector_t **)luaL_checkudata(L, 3, META_SECTOR));
 	//HUDSAFE
 	if (!mo)
 		return LUA_ErrInvalid(L, "mobj_t");
 	if (!rover)
 		return LUA_ErrInvalid(L, "ffloor_t");
-	if (!bound)
-		return LUA_ErrInvalid(L, "sector_t");
-	lua_pushboolean(L, P_CheckSolidLava(mo, rover, bound));
+	lua_pushboolean(L, P_CheckSolidLava(mo, rover));
 	return 1;
 }
 
diff --git a/src/p_local.h b/src/p_local.h
index ce6aed02..1fd7ada0 100644
--- a/src/p_local.h
+++ b/src/p_local.h
@@ -238,7 +238,7 @@ fixed_t P_CameraCeilingZ(camera_t *mobj, sector_t *sector, sector_t *boundsec, f
 
 boolean P_InsideANonSolidFFloor(mobj_t *mobj, ffloor_t *rover);
 boolean P_CheckDeathPitCollide(mobj_t *mo);
-boolean P_CheckSolidLava(mobj_t *mo, ffloor_t *rover, sector_t *bound);
+boolean P_CheckSolidLava(mobj_t *mo, ffloor_t *rover);
 
 mobj_t *P_SpawnMissile(mobj_t *source, mobj_t *dest, mobjtype_t type);
 mobj_t *P_SpawnXYZMissile(mobj_t *source, mobj_t *dest, mobjtype_t type, fixed_t x, fixed_t y, fixed_t z);
diff --git a/src/p_mobj.c b/src/p_mobj.c
index 4f0c8403..6ad84de3 100644
--- a/src/p_mobj.c
+++ b/src/p_mobj.c
@@ -1983,7 +1983,7 @@ static void P_AdjustMobjFloorZ_FFloors(mobj_t *mo, sector_t *sector, UINT8 motyp
 		topheight = P_GetFOFTopZ(mo, sector, rover, mo->x, mo->y, NULL);
 		bottomheight = P_GetFOFBottomZ(mo, sector, rover, mo->x, mo->y, NULL);
 
-		if (mo->player && (P_CheckSolidLava(mo, rover, sector) || P_CanRunOnWater(mo->player, rover))) // only the player should be affected
+		if (mo->player && (P_CheckSolidLava(mo, rover) || P_CanRunOnWater(mo->player, rover))) // only the player should be affected
 			;
 		else if (motype != 0 && rover->flags & FF_SWIMMABLE) // "scenery" only
 			continue;
@@ -2133,15 +2133,23 @@ boolean P_CheckDeathPitCollide(mobj_t *mo)
 	return false;
 }
 
-boolean P_CheckSolidLava(mobj_t *mo, ffloor_t *rover, sector_t *bound)
+boolean P_CheckSolidLava(mobj_t *mo, ffloor_t *rover)
 {
 	I_Assert(mo != NULL);
 	I_Assert(!P_MobjWasRemoved(mo));
 
-	if (rover->flags & FF_SWIMMABLE && GETSECSPECIAL(rover->master->frontsector->special, 1) == 3
-		&& !(rover->master->flags & ML_BLOCKMONSTERS)
-		&& ((rover->master->flags & ML_EFFECT3) || mo->z-mo->momz > P_GetSpecialTopZ(mo, rover->master->frontsector, bound) - FixedMul(16*FRACUNIT, mo->scale)))
-			return true;
+	{
+		fixed_t topheight =
+	#ifdef ESLOPE
+			*rover->t_slope ? P_GetZAt(*rover->t_slope, mo->x, mo->y) :
+	#endif
+			*rover->topheight;
+
+		if (rover->flags & FF_SWIMMABLE && GETSECSPECIAL(rover->master->frontsector->special, 1) == 3
+			&& !(rover->master->flags & ML_BLOCKMONSTERS)
+			&& ((rover->master->flags & ML_EFFECT3) || mo->z-mo->momz > topheight - FixedMul(16*FRACUNIT, mo->scale)))
+				return true;
+	}
 
 	return false;
 }
@@ -3076,11 +3084,17 @@ static boolean P_SceneryZMovement(mobj_t *mo)
 //
 boolean P_CanRunOnWater(player_t *player, ffloor_t *rover)
 {
+	fixed_t topheight =
+#ifdef ESLOPE
+		*rover->t_slope ? P_GetZAt(*rover->t_slope, player->mo->x, player->mo->y) :
+#endif
+		*rover->topheight;
+
 	if (!(player->pflags & PF_NIGHTSMODE) && !player->homing
-		&& (((player->charability == CA_SWIM) || player->powers[pw_super] || player->charflags & SF_RUNONWATER) && player->mo->ceilingz-*rover->topheight >= player->mo->height)
+		&& (((player->charability == CA_SWIM) || player->powers[pw_super] || player->charflags & SF_RUNONWATER) && player->mo->ceilingz-topheight >= player->mo->height)
 		&& (rover->flags & FF_SWIMMABLE) && !(player->pflags & PF_SPINNING) && player->speed > FixedMul(player->runspeed, player->mo->scale)
 		&& !(player->pflags & PF_SLIDING)
-		&& abs(player->mo->z - *rover->topheight) < FixedMul(30*FRACUNIT, player->mo->scale))
+		&& abs(player->mo->z - topheight) < FixedMul(30*FRACUNIT, player->mo->scale))
 		return true;
 
 	return false;