diff --git a/src/lang/english.txt b/src/lang/english.txt
--- a/src/lang/english.txt
+++ b/src/lang/english.txt
@@ -2466,6 +2466,7 @@ STR_NEWGRF_LIST_MISSING                 
 
 # NewGRF 'it's broken' warnings
 STR_NEWGRF_BROKEN                                               :{WHITE}Behaviour of NewGRF '{0:RAW_STRING}' is likely to cause desyncs and/or crashes.
+STR_NEWGRF_BROKEN_POWERED_WAGON                                 :{WHITE}Wagon '{1:ENGINE}' changed powered-wagon state when not inside a depot.
 STR_NEWGRF_BROKEN_VEHICLE_LENGTH                                :{WHITE}It changes vehicle length for '{1:ENGINE}' when not inside a depot.
 STR_BROKEN_VEHICLE_LENGTH                                       :{WHITE}Train '{VEHICLE}' belonging to '{COMPANY}' has invalid length. It is probably caused by problems with NewGRFs. Game may desync or crash.
 
diff --git a/src/newgrf_config.h b/src/newgrf_config.h
--- a/src/newgrf_config.h
+++ b/src/newgrf_config.h
@@ -39,8 +39,9 @@ enum GRFStatus {
 
 /** Encountered GRF bugs */
 enum GRFBugs {
-	GBUG_VEH_LENGTH,  ///< Length of rail vehicle changes when not inside a depot
-	GBUG_VEH_REFIT,   ///< Articulated vehicles carry different cargos resp. are differently refittable than specified in purchase list
+	GBUG_VEH_LENGTH,        ///< Length of rail vehicle changes when not inside a depot
+	GBUG_VEH_REFIT,         ///< Articulated vehicles carry different cargos resp. are differently refittable than specified in purchase list
+	GBUG_VEH_POWERED_WAGON, ///< Powered wagon changed poweredness state when not inside a depot
 };
 
 /** Status of post-gameload GRF compatibility check */
diff --git a/src/rail_cmd.cpp b/src/rail_cmd.cpp
--- a/src/rail_cmd.cpp
+++ b/src/rail_cmd.cpp
@@ -1380,7 +1380,6 @@ static Vehicle *UpdateTrainPowerProc(Veh
 {
 	if (v->type != VEH_TRAIN) return NULL;
 
-	/* Similar checks as in Train::PowerChanged() */
 	TrainList *affected_trains = static_cast<TrainList*>(data);
 	affected_trains->Include(Train::From(v)->First());
 
@@ -1583,8 +1582,7 @@ CommandCost CmdConvertRail(TileIndex til
 	if (flags & DC_EXEC) {
 		/* Railtype changed, update trains as when entering different track */
 		for (Train **v = affected_trains.Begin(); v != affected_trains.End(); v++) {
-			(*v)->PowerChanged();
-			(*v)->UpdateAcceleration();
+			(*v)->RailtypeChanged();
 		}
 	}
 
diff --git a/src/train.h b/src/train.h
--- a/src/train.h
+++ b/src/train.h
@@ -145,6 +145,8 @@ struct Train : public GroundVehicle<Trai
 
 	void ConsistChanged(bool same_length);
 
+	void RailtypeChanged();
+
 	int UpdateSpeed();
 
 	void UpdateAcceleration();
@@ -372,7 +374,7 @@ struct Train : public GroundVehicle<Trai
 
 protected: // These functions should not be called outside acceleration code.
 
-	void UpdateVisualEffect();
+	void UpdateVisualEffect(bool allow_power_change);
 
 	/**
 	 * Allows to know the power value that this vehicle will use.
diff --git a/src/train_cmd.cpp b/src/train_cmd.cpp
--- a/src/train_cmd.cpp
+++ b/src/train_cmd.cpp
@@ -130,10 +130,27 @@ void CheckTrainsLengths()
 }
 
 /**
- * Update the cached visual effect.
+ * Update visual effect, power and acceleration caches.
+ * Called when a vehicle in the consist enters a different railtype.
  */
-void Train::UpdateVisualEffect()
+void Train::RailtypeChanged()
 {
+	for (Train *u = this; u != NULL; u = u->Next()) {
+		/* The wagon-is-powered-state should not change, so the weight does not change. */
+		u->UpdateVisualEffect(false);
+	}
+	this->PowerChanged();
+	if (this->IsFrontEngine()) this->UpdateAcceleration();
+}
+
+/**
+ * Update the cached visual effect.
+ * @param allow_power_change true if the wagon-is-powered-state may change.
+ */
+void Train::UpdateVisualEffect(bool allow_power_change)
+{
+	byte powered_before = this->tcache.cached_vis_effect & 0x80;
+
 	const Engine *e = Engine::Get(this->engine_type);
 	if (e->u.rail.visual_effect != 0) {
 		this->tcache.cached_vis_effect = e->u.rail.visual_effect;
@@ -156,6 +173,11 @@ void Train::UpdateVisualEffect()
 
 		if (callback != CALLBACK_FAILED) this->tcache.cached_vis_effect = GB(callback, 0, 8);
 	}
+
+	if (!allow_power_change && powered_before != (this->tcache.cached_vis_effect & 0x80)) {
+		this->tcache.cached_vis_effect ^= 0x80;
+		ShowNewGrfVehicleError(this->engine_type, STR_NEWGRF_BROKEN, STR_NEWGRF_BROKEN_POWERED_WAGON, GBUG_VEH_POWERED_WAGON, false);
+	}
 }
 
 /**
@@ -215,7 +237,7 @@ void Train::ConsistChanged(bool same_len
 		u->colourmap = PAL_NONE;
 
 		/* Update powered-wagon-status and visual effect */
-		u->UpdateVisualEffect();
+		u->UpdateVisualEffect(true);
 
 		if (rvi_v->pow_wag_power != 0 && rvi_u->railveh_type == RAILVEH_WAGON &&
 				UsesWagonOverride(u) && !HasBit(u->tcache.cached_vis_effect, 7)) {
@@ -1566,7 +1588,7 @@ static void ReverseTrainSwapVeh(Train *v
 	}
 
 	/* Update power of the train in case tiles were different rail type. */
-	v->PowerChanged();
+	v->RailtypeChanged();
 }
 
 
@@ -3367,8 +3389,7 @@ static void TrainController(Train *v, Ve
 					v->tile = gp.new_tile;
 
 					if (GetTileRailType(gp.new_tile) != GetTileRailType(gp.old_tile)) {
-						v->First()->PowerChanged();
-						v->First()->UpdateAcceleration();
+						v->First()->RailtypeChanged();
 					}
 
 					v->track = chosen_track;