diff --git a/src/newgrf.cpp b/src/newgrf.cpp
index 395212a916..0a70a41d41 100644
--- a/src/newgrf.cpp
+++ b/src/newgrf.cpp
@@ -1223,7 +1223,7 @@ static ChangeInfoResult StationChangeInfo(uint stid, int numinfo, int prop, Byte
 						DrawTileSeqStruct *dtss = const_cast<DrawTileSeqStruct *>(&dts->seq[seq_count - 1]);
 
 						dtss->delta_x = buf->ReadByte();
-						if ((byte) dtss->delta_x == 0x80) break;
+						if (dtss->IsTerminator()) break;
 						dtss->delta_y = buf->ReadByte();
 						dtss->delta_z = buf->ReadByte();
 						dtss->size_x = buf->ReadByte();
@@ -3955,7 +3955,7 @@ static void NewSpriteGroup(ByteReader *buf)
 
 						if (type > 0) {
 							seq->delta_z = buf->ReadByte();
-							if ((byte)seq->delta_z == 0x80) continue;
+							if (!seq->IsParentSprite()) continue;
 						}
 
 						seq->size_x = buf->ReadByte();
@@ -3964,7 +3964,7 @@ static void NewSpriteGroup(ByteReader *buf)
 					}
 
 					/* Set the terminator value. */
-					const_cast<DrawTileSeqStruct *>(group->dts->seq)[i].delta_x = (int8)0x80;
+					const_cast<DrawTileSeqStruct *>(group->dts->seq)[i].MakeTerminator();
 
 					break;
 				}
diff --git a/src/sprite.cpp b/src/sprite.cpp
index df4eec8efb..2e453941a5 100644
--- a/src/sprite.cpp
+++ b/src/sprite.cpp
@@ -43,7 +43,7 @@ void DrawCommonTileSeq(const TileInfo *ti, const DrawTileSprites *dts, Transpare
 
 		PaletteID pal = SpriteLayoutPaletteTransform(image, dtss->image.pal, default_palette);
 
-		if ((byte)dtss->delta_z != 0x80) {
+		if (dtss->IsParentSprite()) {
 			parent_sprite_encountered = true;
 			AddSortableSpriteToDraw(
 				image, pal,
@@ -94,7 +94,7 @@ void DrawCommonTileSeqInGUI(int x, int y, const DrawTileSprites *dts, int32 orig
 
 		PaletteID pal = SpriteLayoutPaletteTransform(image, dtss->image.pal, default_palette);
 
-		if ((byte)dtss->delta_z != 0x80) {
+		if (dtss->IsParentSprite()) {
 			Point pt = RemapCoords(dtss->delta_x, dtss->delta_y, dtss->delta_z);
 			DrawSprite(image, pal, x + pt.x, y + pt.y);
 
diff --git a/src/sprite.h b/src/sprite.h
index 5d1c7f07be..3e03aee6ab 100644
--- a/src/sprite.h
+++ b/src/sprite.h
@@ -27,11 +27,29 @@
 struct DrawTileSeqStruct {
 	int8 delta_x; ///< \c 0x80 is sequence terminator
 	int8 delta_y;
-	int8 delta_z;
+	int8 delta_z; ///< \c 0x80 identifies child sprites
 	byte size_x;
 	byte size_y;
 	byte size_z;
 	PalSpriteID image;
+
+	/** Make this struct a sequence terminator. */
+	void MakeTerminator()
+	{
+		this->delta_x = (int8)0x80;
+	}
+
+	/** Check whether this is a sequence terminator. */
+	bool IsTerminator() const
+	{
+		return (byte)this->delta_x == 0x80;
+	}
+
+	/** Check whether this is a parent sprite with a boundingbox. */
+	bool IsParentSprite() const
+	{
+		return (byte)this->delta_z != 0x80;
+	}
 };
 
 /** Ground palette sprite of a tile, together with its child sprites */
@@ -56,7 +74,7 @@ struct DrawBuildingsTileStruct {
 };
 
 /** Iterate through all DrawTileSeqStructs in DrawTileSprites. */
-#define foreach_draw_tile_seq(idx, list) for (idx = list; ((byte) idx->delta_x) != 0x80; idx++)
+#define foreach_draw_tile_seq(idx, list) for (idx = list; !idx->IsTerminator(); idx++)
 
 void DrawCommonTileSeq(const struct TileInfo *ti, const DrawTileSprites *dts, TransparencyOption to, int32 orig_offset, uint32 newgrf_offset, PaletteID default_palette, bool child_offset_is_unsigned);
 void DrawCommonTileSeqInGUI(int x, int y, const DrawTileSprites *dts, int32 orig_offset, uint32 newgrf_offset, PaletteID default_palette, bool child_offset_is_unsigned);