diff --git a/src/g_shared/a_skies.cpp b/src/g_shared/a_skies.cpp
index d62a2a07bd..54661ea147 100644
--- a/src/g_shared/a_skies.cpp
+++ b/src/g_shared/a_skies.cpp
@@ -186,10 +186,12 @@ void ASkyPicker::PostBeginPlay ()
 		if (0 == (args[1] & 2))
 		{
 			Sector->CeilingSkyBox = box;
+			if (box == NULL) Sector->MoreFlags |= SECF_NOCEILINGSKYBOX;	// sector should ignore the level's default skybox
 		}
 		if (0 == (args[1] & 1))
 		{
 			Sector->FloorSkyBox = box;
+			if (box == NULL) Sector->MoreFlags |= SECF_NOFLOORSKYBOX;	// sector should ignore the level's default skybox
 		}
 	}
 	Destroy ();
diff --git a/src/p_sectors.cpp b/src/p_sectors.cpp
index 904c76c1b3..bc7abd3805 100644
--- a/src/p_sectors.cpp
+++ b/src/p_sectors.cpp
@@ -29,6 +29,7 @@
 #include "po_man.h"
 #include "farchive.h"
 #include "r_utility.h"
+#include "a_sharedglobal.h"
 #include "r_data/colormaps.h"
 
 
@@ -800,6 +801,20 @@ int sector_t::GetCeilingLight () const
 	}
 }
 
+
+ASkyViewpoint *sector_t::GetSkyBox(int which)
+{
+	if (which == floor)
+	{
+		return FloorSkyBox != NULL ? FloorSkyBox : (MoreFlags & SECF_NOFLOORSKYBOX)? (ASkyViewpoint*)NULL : level.DefaultSkybox;
+	}
+	else
+	{
+		return CeilingSkyBox != NULL ? CeilingSkyBox : (MoreFlags & SECF_NOCEILINGSKYBOX)? (ASkyViewpoint*)NULL : level.DefaultSkybox;
+	}
+}
+
+
 sector_t *sector_t::GetHeightSec() const 
 {
 	if (heightsec == NULL)
diff --git a/src/r_bsp.cpp b/src/r_bsp.cpp
index bf0ac910fa..545d009d98 100644
--- a/src/r_bsp.cpp
+++ b/src/r_bsp.cpp
@@ -1087,7 +1087,8 @@ void R_Subsector (subsector_t *sub)
 		basecolormap = frontsector->ColorMap;
 	}
 
-	skybox = frontsector->CeilingSkyBox != NULL ? frontsector->CeilingSkyBox : level.DefaultSkybox;
+	skybox = frontsector->GetSkyBox(sector_t::ceiling);
+
 	ceilingplane = frontsector->ceilingplane.PointOnSide(viewx, viewy, viewz) > 0 ||
 		frontsector->GetTexture(sector_t::ceiling) == skyflatnum ||
 		(skybox != NULL && skybox->bAlways) ||
@@ -1127,7 +1128,7 @@ void R_Subsector (subsector_t *sub)
 	// killough 3/7/98: Add (x,y) offsets to flats, add deep water check
 	// killough 3/16/98: add floorlightlevel
 	// killough 10/98: add support for skies transferred from sidedefs
-	skybox = frontsector->FloorSkyBox != NULL ? frontsector->FloorSkyBox : level.DefaultSkybox;
+	skybox = frontsector->GetSkyBox(sector_t::floor);
 	floorplane = frontsector->floorplane.PointOnSide(viewx, viewy, viewz) > 0 || // killough 3/7/98
 		frontsector->GetTexture(sector_t::floor) == skyflatnum ||
 		(skybox != NULL && skybox->bAlways) ||
diff --git a/src/r_defs.h b/src/r_defs.h
index afda92089d..a93622b416 100644
--- a/src/r_defs.h
+++ b/src/r_defs.h
@@ -340,6 +340,8 @@ enum
 	SECF_UNDERWATERMASK	= 32+64,
 	SECF_DRAWN			= 128,	// sector has been drawn at least once
 	SECF_HIDDEN			= 256,	// Do not draw on textured automap
+	SECF_NOFLOORSKYBOX	= 512,	// force use of regular sky 
+	SECF_NOCEILINGSKYBOX	= 1024,	// force use of regular sky 
 };
 
 enum
@@ -451,6 +453,8 @@ struct sector_t
 	DInterpolation *SetInterpolation(int position, bool attach);
 	void StopInterpolation(int position);
 
+	ASkyViewpoint *GetSkyBox(int which);
+
 	enum
 	{
 		floor,