diff --git a/src/playsim/actor.h b/src/playsim/actor.h
index 326a6f1867..f516b79f1e 100644
--- a/src/playsim/actor.h
+++ b/src/playsim/actor.h
@@ -873,7 +873,7 @@ public:
 	void PlayPushSound();
 
 	// Called when an actor with MF_MISSILE and MF2_FLOORBOUNCE hits the floor
-	bool FloorBounceMissile (secplane_t &plane);
+	bool FloorBounceMissile (secplane_t &plane, bool is3DFloor);
 
 	// Called by RoughBlockCheck
 	bool IsOkayToAttack (AActor *target);
diff --git a/src/playsim/p_map.cpp b/src/playsim/p_map.cpp
index f8b23a8118..84accbe760 100644
--- a/src/playsim/p_map.cpp
+++ b/src/playsim/p_map.cpp
@@ -2486,7 +2486,9 @@ bool P_TryMove(AActor *thing, const DVector2 &pos,
 						// If it's a bouncer, let it bounce off its new floor, too.
 						if (thing->BounceFlags & BOUNCE_Floors)
 						{
-							thing->FloorBounceMissile(tm.floorsector->floorplane);
+							F3DFloor* ff = nullptr;
+							NextLowestFloorAt(tm.sector, tm.pos.X, tm.pos.Y, tm.pos.Z, 0, thing->MaxStepHeight, nullptr, &ff);
+							thing->FloorBounceMissile(ff != nullptr ? *ff->top.plane : tm.floorsector->floorplane, ff != nullptr);
 						}
 						else
 						{
@@ -3603,14 +3605,17 @@ bool FSlide::BounceWall(AActor *mo)
 	{ // Could not find a wall, so bounce off the floor/ceiling instead.
 		double floordist = mo->Z() - mo->floorz;
 		double ceildist = mo->ceilingz - mo->Z();
+		F3DFloor* ff = nullptr;
 		if (floordist <= ceildist)
 		{
-			mo->FloorBounceMissile(mo->Sector->floorplane);
+			NextLowestFloorAt(mo->Sector, mo->X(), mo->Y(), mo->Z(), 0, mo->MaxStepHeight, nullptr, &ff);
+			mo->FloorBounceMissile(ff != nullptr ? *ff->top.plane : mo->floorsector->floorplane, ff != nullptr);
 			return true;
 		}
 		else
 		{
-			mo->FloorBounceMissile(mo->Sector->ceilingplane);
+			NextHighestCeilingAt(mo->Sector, mo->X(), mo->Y(), mo->Z(), mo->Top(), 0, nullptr, &ff);
+			mo->FloorBounceMissile(ff != nullptr ? *ff->bottom.plane : mo->ceilingsector->ceilingplane, ff != nullptr);
 			return true;
 		}
 	}
diff --git a/src/playsim/p_mobj.cpp b/src/playsim/p_mobj.cpp
index acc18902ab..e25545f804 100644
--- a/src/playsim/p_mobj.cpp
+++ b/src/playsim/p_mobj.cpp
@@ -1732,7 +1732,7 @@ void AActor::PlayBounceSound(bool onfloor)
 // Returns true if the missile was destroyed
 //----------------------------------------------------------------------------
 
-bool AActor::FloorBounceMissile (secplane_t &plane)
+bool AActor::FloorBounceMissile (secplane_t &plane, bool is3DFloor)
 {
 	if (flags & MF_MISSILE)
 	{
@@ -1808,11 +1808,15 @@ bool AActor::FloorBounceMissile (secplane_t &plane)
 		return true;
 	}
 
-	double dot = (Vel | plane.Normal()) * 2;
+	DVector3 norm = plane.Normal();
+	if (is3DFloor)
+		norm = -norm;
+
+	double dot = (Vel | norm) * 2;
 
 	if (BounceFlags & (BOUNCE_HereticType | BOUNCE_MBF))
 	{
-		Vel -= plane.Normal() * dot;
+		Vel -= norm * dot;
 		AngleFromVel();
 		if (!(BounceFlags & BOUNCE_MBF)) // Heretic projectiles die, MBF projectiles don't.
 		{
@@ -1826,7 +1830,7 @@ bool AActor::FloorBounceMissile (secplane_t &plane)
 	else // Don't run through this for MBF-style bounces
 	{
 		// The reflected velocity keeps only about 70% of its original speed
-		Vel = (Vel - plane.Normal() * dot) * bouncefactor;
+		Vel = (Vel - norm * dot) * bouncefactor;
 		AngleFromVel();
 	}
 
@@ -1850,10 +1854,10 @@ bool AActor::FloorBounceMissile (secplane_t &plane)
 	}
 	else if (BounceFlags & (BOUNCE_AutoOff|BOUNCE_AutoOffFloorOnly))
 	{
-		if (plane.fC() > 0 || (BounceFlags & BOUNCE_AutoOff))
+		if (norm.Z > 0 || (BounceFlags & BOUNCE_AutoOff))
 		{
 			// AutoOff only works when bouncing off a floor, not a ceiling (or in compatibility mode.)
-			if (!(flags & MF_NOGRAVITY) && (Vel.Z < 3))
+			if (!(flags & MF_NOGRAVITY) && ((Vel | norm) < 3))
 				BounceFlags &= ~BOUNCE_TypeMask;
 		}
 	}
@@ -2646,7 +2650,9 @@ static void P_ZMovement (AActor *mo, double oldfloorz)
 				mo->SetZ(mo->floorz);
 				if (mo->BounceFlags & BOUNCE_Floors)
 				{
-					mo->FloorBounceMissile (mo->floorsector->floorplane);
+					F3DFloor* ff = nullptr;
+					NextLowestFloorAt(mo->Sector, mo->X(), mo->Y(), mo->Z(), 0, mo->MaxStepHeight, nullptr, &ff);
+					mo->FloorBounceMissile (ff != nullptr ? *ff->top.plane : mo->floorsector->floorplane, ff != nullptr);
 					/* if (!CanJump(mo)) */ return;
 				}
 				else if (mo->flags3 & MF3_NOEXPLODEFLOOR)
@@ -2682,7 +2688,9 @@ static void P_ZMovement (AActor *mo, double oldfloorz)
 			}
 			else if (mo->BounceFlags & BOUNCE_MBF && mo->Vel.Z) // check for MBF-like bounce on non-missiles
 			{
-				mo->FloorBounceMissile(mo->floorsector->floorplane);
+				F3DFloor* ff = nullptr;
+				NextLowestFloorAt(mo->Sector, mo->X(), mo->Y(), mo->Z(), 0, mo->MaxStepHeight, nullptr, &ff);
+				mo->FloorBounceMissile(ff != nullptr ? *ff->top.plane : mo->floorsector->floorplane, ff != nullptr);
 			}
 			if (mo->flags3 & MF3_ISMONSTER)		// Blasted mobj falling
 			{
@@ -2753,7 +2761,9 @@ static void P_ZMovement (AActor *mo, double oldfloorz)
 			mo->SetZ(mo->ceilingz - mo->Height);
 			if (mo->BounceFlags & BOUNCE_Ceilings)
 			{	// ceiling bounce
-				mo->FloorBounceMissile (mo->ceilingsector->ceilingplane);
+				F3DFloor* ff = nullptr;
+				NextHighestCeilingAt(mo->Sector, mo->X(), mo->Y(), mo->Z(), mo->Top(), 0, nullptr, &ff);
+				mo->FloorBounceMissile(ff != nullptr ? *ff->bottom.plane : mo->ceilingsector->ceilingplane, ff != nullptr);
 				/* if (!CanJump(mo)) */ return;
 			}
 			if (mo->flags & MF_SKULLFLY)
diff --git a/src/scripting/vmthunks_actors.cpp b/src/scripting/vmthunks_actors.cpp
index 18cd8aa32f..2cf04fd80a 100644
--- a/src/scripting/vmthunks_actors.cpp
+++ b/src/scripting/vmthunks_actors.cpp
@@ -1851,8 +1851,9 @@ DEFINE_ACTION_FUNCTION(AActor, BouncePlane)
 {
 	PARAM_SELF_PROLOGUE(AActor);
 	PARAM_POINTER(plane, secplane_t);
+	PARAM_BOOL(is3DFloor);
 
-	ACTION_RETURN_BOOL(self->FloorBounceMissile(*plane));
+	ACTION_RETURN_BOOL(self->FloorBounceMissile(*plane, is3DFloor));
 }
 
 DEFINE_ACTION_FUNCTION(AActor, PlayBounceSound)
diff --git a/wadsrc/static/zscript/actors/actor.zs b/wadsrc/static/zscript/actors/actor.zs
index 37b36e9e7c..e0633d599b 100644
--- a/wadsrc/static/zscript/actors/actor.zs
+++ b/wadsrc/static/zscript/actors/actor.zs
@@ -866,7 +866,7 @@ class Actor : Thinker native
 	native void PlayPushSound();
 	native bool BounceActor(Actor blocking, bool onTop);
 	native bool BounceWall(Line l = null);
-	native bool BouncePlane(readonly<SecPlane> plane);
+	native bool BouncePlane(readonly<SecPlane> plane, bool is3DFloor = false);
 	native void PlayBounceSound(bool onFloor);
 	native bool ReflectOffActor(Actor blocking);