diff --git a/geom/inc/TGeoBuilder.h b/geom/inc/TGeoBuilder.h
index 0f05103e0f4ebc8c2bd96d2d451d0e492ccdd21a..2546e743958faefcd54f699311e6a590edf7e4c8 100644
--- a/geom/inc/TGeoBuilder.h
+++ b/geom/inc/TGeoBuilder.h
@@ -26,8 +26,12 @@
 
 class TGeoMaterial;
 class TGeoMatrix;
+class TGeoMedium;
 class TGeoShape;
 class TGeoVolume;
+class TGeoVolumeAssembly;
+class TGeoVolumeMulti;
+class TGeoManager;
 
 class TGeoBuilder : public TObject
 {