diff --git a/src/signs_cmd.cpp b/src/signs_cmd.cpp
--- a/src/signs_cmd.cpp
+++ b/src/signs_cmd.cpp
@@ -16,6 +16,7 @@
 #include "signs_func.h"
 #include "command_func.h"
 #include "tilehighlight_func.h"
+#include "viewport_kdtree.h"
 #include "window_func.h"
 #include "string_func.h"
 
@@ -57,7 +58,7 @@ CommandCost CmdPlaceSign(TileIndex tile,
 		if (!StrEmpty(text)) {
 			si->name = stredup(text);
 		}
-		si->UpdateVirtCoord();
+		_viewport_sign_kdtree.Insert(ViewportSignKdtreeItem::MakeSign(si->index));
 		InvalidateWindowData(WC_SIGN_LIST, 0, 0);
 		_new_sign_id = si->index;
 	}
@@ -98,7 +99,7 @@ CommandCost CmdRenameSign(TileIndex tile
 		}
 	} else { // Delete sign
 		if (flags & DC_EXEC) {
-			si->sign.MarkDirty();
+			_viewport_sign_kdtree.Remove(ViewportSignKdtreeItem::MakeSign(si->index));
 			delete si;
 
 			InvalidateWindowData(WC_SIGN_LIST, 0, 0);