diff --git a/render_povray/render.py b/render_povray/render.py
index 0a8d1d90bc0dbf55c7454cc28d602d14b204f8dd..6150cc4f730b5b3177f0a935e2c3c451224fc4a8 100644
--- a/render_povray/render.py
+++ b/render_povray/render.py
@@ -753,7 +753,7 @@ def write_pov(filename, scene=None, info_callback=None):
                         uvs = uv.uv1, uv.uv2, uv.uv3
 
                     for uv in uvs:
-                        uniqueUVs[tuple(uv)] = [-1]
+                        uniqueUVs[uv[:]] = [-1]
 
                 tabWrite('uv_vectors {\n')
                 #print unique_uvs