diff --git a/roadveh_gui.c b/roadveh_gui.c
index 23c4758f19..06737a5019 100644
--- a/roadveh_gui.c
+++ b/roadveh_gui.c
@@ -512,7 +512,9 @@ static void DrawRoadDepotWindow(Window *w)
 	SetVScrollCount(w, (num + w->hscroll.cap - 1) / w->hscroll.cap);
 
 	/* locate the depot struct */
-	for(d=_depots; d->xy != (TileIndex)tile; d++) {}
+	for (d = _depots; d->xy != (TileIndex)tile; d++) {
+		assert(d < endof(_depots);
+	}
 
 	SetDParam(0, d->town_index);
 	DrawWindowWidgets(w);
diff --git a/ship_gui.c b/ship_gui.c
index 959cbd0ec8..e90077aed6 100644
--- a/ship_gui.c
+++ b/ship_gui.c
@@ -646,7 +646,9 @@ static void DrawShipDepotWindow(Window *w)
 	SetVScrollCount(w, (num + w->hscroll.cap - 1) / w->hscroll.cap);
 
 	/* locate the depot struct */
-	for(d=_depots; d->xy != (TileIndex)tile; d++) {}
+	for (d = _depots; d->xy != (TileIndex)tile; d++) {
+		assert(d < endof(_depots);
+	}
 
 	SetDParam(0, d->town_index);
 	DrawWindowWidgets(w);
diff --git a/train_gui.c b/train_gui.c
index 41335d1b51..b590eb29b6 100644
--- a/train_gui.c
+++ b/train_gui.c
@@ -333,7 +333,9 @@ static void DrawTrainDepotWindow(Window *w)
 	SetHScrollCount(w, hnum);
 
 	/* locate the depot struct */
-	for(d=_depots; d->xy != (TileIndex)tile; d++) {}
+	for (d = _depots; d->xy != (TileIndex)tile; d++) {
+		assert(d < endof(_depots);
+	}
 
 	SetDParam(0, d->town_index);
 	DrawWindowWidgets(w);