diff --git a/src/roadveh_gui.cpp b/src/roadveh_gui.cpp
--- a/src/roadveh_gui.cpp
+++ b/src/roadveh_gui.cpp
@@ -145,6 +145,8 @@ static void RoadVehDetailsWndProc(Window
 
 					if (!first) strecat(capacity, ", ", lastof(capacity));
 					strecat(capacity, buffer, lastof(capacity));
+
+					first = false;
 				}
 			}