diff --git a/src/newgrf_debug_gui.cpp b/src/newgrf_debug_gui.cpp
--- a/src/newgrf_debug_gui.cpp
+++ b/src/newgrf_debug_gui.cpp
@@ -35,6 +35,7 @@
 
 #include "table/strings.h"
 
+/** The sprite picker. */
 NewGrfDebugSpritePicker _newgrf_debug_sprite_picker = { SPM_NONE, NULL, 0, SmallVector<SpriteID, 256>() };
 
 /**