diff --git a/nlmod/read/geotop.py b/nlmod/read/geotop.py
index 89ad01cf..7aaf5c37 100644
--- a/nlmod/read/geotop.py
+++ b/nlmod/read/geotop.py
@@ -36,7 +36,7 @@ def get_lithok_colors():
         8: (216, 163, 32),
         9: (95, 95, 255),
     }
-    colors = {key: (x / 255 for x in color) for key, color in colors.items()}
+    colors = {key: (x / 255 for x in color,) for key, color in colors.items()}
     return colors