diff --git a/src/engine.cpp b/src/engine.cpp
index b9479d82f2..63f391d223 100644
--- a/src/engine.cpp
+++ b/src/engine.cpp
@@ -927,6 +927,8 @@ void EnginesMonthlyLoop()
 				}
 			}
 		}
+
+		InvalidateWindowClassesData(WC_BUILD_VEHICLE); // rebuild the purchase list (esp. when sorted by reliability)
 	}
 }