diff --git a/src/settings.cpp b/src/settings.cpp
--- a/src/settings.cpp
+++ b/src/settings.cpp
@@ -751,7 +751,7 @@ static bool TrainAccelerationModelChange
 
 static bool DragSignalsDensityChanged(int32)
 {
-	SetWindowDirty(WC_BUILD_SIGNAL, 0);
+	InvalidateWindowData(WC_BUILD_SIGNAL, 0);
 
 	return true;
 }