diff --git a/src/pathfinder/yapf/yapf_costrail.hpp b/src/pathfinder/yapf/yapf_costrail.hpp
index d9d89b12fa..22103987ad 100644
--- a/src/pathfinder/yapf/yapf_costrail.hpp
+++ b/src/pathfinder/yapf/yapf_costrail.hpp
@@ -418,9 +418,16 @@ no_entry_cost: // jump here at the beginning if the node has no parent (it is th
 					CFollowTrackRail ft(v);
 					TileIndex t = cur.tile;
 					Trackdir td = cur.td;
+					/* Arbitrary maximum tiles to follow to avoid infinite loops. */
+					uint max_tiles = 20;
 					while (ft.Follow(t, td)) {
 						assert(t != ft.m_new_tile);
 						t = ft.m_new_tile;
+						if (t == cur.tile || --max_tiles == 0) {
+							/* We looped back on ourself or found another loop, bail out. */
+							td = INVALID_TRACKDIR;
+							break;
+						}
 						if (KillFirstBit(ft.m_new_td_bits) != TRACKDIR_BIT_NONE) {
 							/* We encountered a junction; it's going to be too complex to
 							 * handle this perfectly, so just bail out. There is no simple