diff --git a/source/common/objects/dobjgc.cpp b/source/common/objects/dobjgc.cpp
index d388e4836b..c2fe53bbe0 100644
--- a/source/common/objects/dobjgc.cpp
+++ b/source/common/objects/dobjgc.cpp
@@ -184,8 +184,15 @@ static cycle_t GCTime;			// Track time spent in GC
 //
 //==========================================================================
 
+TArray<DObject*> allObjects;
+
 void CheckGC()
 {
+	allObjects.Clear();
+	for (auto obj = GC::Root; obj; obj = obj->ObjNext)
+	{
+		allObjects.Push(obj);
+	}
 	AllocHistory.AddAlloc(RunningAllocBytes);
 	RunningAllocBytes = 0;
 	if (State > GCS_Pause || AllocBytes >= Threshold)
@@ -219,6 +226,7 @@ void SetThreshold()
 size_t PropagateMark()
 {
 	DObject *obj = Gray;
+	assert(!obj || allObjects.Find(obj) < allObjects.Size());
 	assert(obj->IsGray());
 	obj->Gray2Black();
 	Gray = obj->GCNext;
@@ -319,6 +327,8 @@ void Mark(DObject **obj)
 {
 	DObject *lobj = *obj;
 
+	assert(!lobj || allObjects.Find(lobj) < allObjects.Size());
+
 	//assert(lobj == nullptr || !(lobj->ObjectFlags & OF_Released));
 	if (lobj != nullptr && !(lobj->ObjectFlags & OF_Released))
 	{
diff --git a/source/games/duke/src/player_r.cpp b/source/games/duke/src/player_r.cpp
index 371fce386c..7be3cac504 100644
--- a/source/games/duke/src/player_r.cpp
+++ b/source/games/duke/src/player_r.cpp
@@ -1215,7 +1215,7 @@ static void movement(DDukePlayer* const p, ESyncBits actions, sectortype* psect,
 			if (pact->getOffsetZ() + p->vel.Z  >= floorz - i) // hit the ground
 			{
 				S_StopSound(DUKE_SCREAM, pact);
-				if (!p->insector() || p->cursector->lotag != 1)
+				if (!p->insector() || p->cursector->lotag != ST_1_ABOVE_WATER)
 				{
 					if (isRRRA()) p->MotoOnGround = 1;
 					if ((p->falling_counter > 62 || (isRRRA() && p->falling_counter > 2 && p->insector() && p->cursector->lotag == 802)) && !ud.god)