diff --git a/lib/gpt/ml/layer/linear.py b/lib/gpt/ml/layer/linear.py
index b21cc30b..49bdceea 100644
--- a/lib/gpt/ml/layer/linear.py
+++ b/lib/gpt/ml/layer/linear.py
@@ -80,10 +80,12 @@ def _contract(self, w, f):
         return ret
 
     def __call__(self, weights, layer_input):
+        layer_input = g.util.to_list(layer_input)
         w = self._get_weight_list(weights)
         return self._contract(w, layer_input)
 
     def projected_gradient_adj(self, weights, layer_input, left):
+        layer_input = g.util.to_list(layer_input)
         left = g.util.to_list(left)
 
         assert len(weights) == 1