diff --git a/src/tbtr_template_gui_create.cpp b/src/tbtr_template_gui_create.cpp
index a21c168636..42dd41c647 100644
--- a/src/tbtr_template_gui_create.cpp
+++ b/src/tbtr_template_gui_create.cpp
@@ -188,6 +188,9 @@ public:
 		}
 
 		virtual_train = train;
+		if (virtual_train != NULL) {
+			assert(HasBit(virtual_train->subtype, GVSF_VIRTUAL));
+		}
 		UpdateButtonState();
 	}
 
@@ -542,6 +545,7 @@ public:
 	void RearrangeVirtualTrain()
 	{
 		virtual_train = virtual_train->First();
+		assert(HasBit(virtual_train->subtype, GVSF_VIRTUAL));
 	}
 
 
diff --git a/src/train_cmd.cpp b/src/train_cmd.cpp
index 677401bca1..4f92b0ad5d 100644
--- a/src/train_cmd.cpp
+++ b/src/train_cmd.cpp
@@ -1211,6 +1211,7 @@ CommandCost CmdMoveRailVehicle(TileIndex tile, DoCommandFlag flags, uint32 p1, u
 	src = src->GetFirstEnginePart();
 	if (dst != NULL) {
 		dst = dst->GetFirstEnginePart();
+		assert(HasBit(dst->subtype, GVSF_VIRTUAL) == HasBit(src->subtype, GVSF_VIRTUAL));
 	}
 
 	/* don't move the same vehicle.. */
@@ -1218,9 +1219,11 @@ CommandCost CmdMoveRailVehicle(TileIndex tile, DoCommandFlag flags, uint32 p1, u
 
 	/* locate the head of the two chains */
 	Train *src_head = src->First();
+	assert(HasBit(src_head->subtype, GVSF_VIRTUAL) == HasBit(src->subtype, GVSF_VIRTUAL));
 	Train *dst_head;
 	if (dst != NULL) {
 		dst_head = dst->First();
+		assert(HasBit(dst_head->subtype, GVSF_VIRTUAL) == HasBit(dst->subtype, GVSF_VIRTUAL));
 		if (dst_head->tile != src_head->tile) return CMD_ERROR;
 		/* Now deal with articulated part of destination wagon */
 		dst = dst->GetLastEnginePart();
diff --git a/src/vehicle.cpp b/src/vehicle.cpp
index 5774aa7c0f..bab123360d 100644
--- a/src/vehicle.cpp
+++ b/src/vehicle.cpp
@@ -1072,6 +1072,8 @@ void CallVehicleTicks()
 	for (TemplateReplacementMap::iterator it = _vehicles_to_templatereplace.Begin(); it != _vehicles_to_templatereplace.End(); it++) {
 		Train *t = it->first;
 
+		assert(!_vehicles_to_autoreplace.Contains(t));
+
 		/* Store the position of the effect as the vehicle pointer will become invalid later */
 		int x = t->x_pos;
 		int y = t->y_pos;