diff --git a/src/p_floor.cpp b/src/p_floor.cpp
index 1bd0c53fc..8f7d935ee 100644
--- a/src/p_floor.cpp
+++ b/src/p_floor.cpp
@@ -640,6 +640,7 @@ bool EV_BuildStairs (int tag, DFloor::EStair type, line_t *line,
 		floor->m_Delay = delay;
 		floor->m_PauseTime = 0;
 		floor->m_StepTime = floor->m_PerStepTime = persteptime;
+		floor->m_Instant = false;
 
 		floor->m_Crush = (usespecials & DFloor::stairCrush) ? 10 : -1; //jff 2/27/98 fix uninitialized crush field
 		floor->m_Hexencrush = false;
@@ -755,6 +756,7 @@ bool EV_BuildStairs (int tag, DFloor::EStair type, line_t *line,
 				//jff 2/27/98 fix uninitialized crush field
 				floor->m_Crush = (!(usespecials & DFloor::stairUseSpecials) && speed == 4) ? 10 : -1; //jff 2/27/98 fix uninitialized crush field
 				floor->m_Hexencrush = false;
+				floor->m_Instant = false;
 				floor->m_ResetCount = reset;	// [RH] Tics until reset (0 if never)
 				floor->m_OrgDist = sec->floorplane.fD();	// [RH] Height to reset to
 			}
@@ -817,6 +819,7 @@ bool EV_DoDonut (int tag, line_t *line, double pillarspeed, double slimespeed)
 			floor->m_Direction = 1;
 			floor->m_Sector = s2;
 			floor->m_Speed = slimespeed;
+			floor->m_Instant = false;
 			floor->m_Texture = s3->GetTexture(sector_t::floor);
 			floor->m_NewSpecial.Clear();
 			height = s3->FindHighestFloorPoint (&spot);
@@ -831,6 +834,7 @@ bool EV_DoDonut (int tag, line_t *line, double pillarspeed, double slimespeed)
 			floor->m_Direction = -1;
 			floor->m_Sector = s1;
 			floor->m_Speed = pillarspeed;
+			floor->m_Instant = false;
 			height = s3->FindHighestFloorPoint (&spot);
 			floor->m_FloorDestDist = s1->floorplane.PointToDist (spot, height);
 			floor->StartFloorSound ();