diff --git a/Lib/fontTools/ttLib/tables/_g_l_y_f.py b/Lib/fontTools/ttLib/tables/_g_l_y_f.py
index 9901a6331..f5ab386d5 100644
--- a/Lib/fontTools/ttLib/tables/_g_l_y_f.py
+++ b/Lib/fontTools/ttLib/tables/_g_l_y_f.py
@@ -579,6 +579,7 @@ class Glyph:
 				else:
 					move = compo.x, compo.y
 				
+				coordinates = GlyphCoordinates(coordinates)
 				if not hasattr(compo, "transform"):
 					coordinates.translate(move)
 				else: