Unrecognized type 'UOverlay' - type must be a UCLASS, USTRUCT or UENUM

Why? If UOverlay is declared as UCLASS in UMG?

/**
 * Allows widgets to be stacked on top of each other, uses simple flow layout for content on each layer.
 */
UCLASS()
class UMG_API UOverlay : public UPanelWidget
{

How can I accept reference to a Overlay Panel widget in my blueprint function?

I know, I forgot to add UMG to my Build.cs PublicDependencyModule.