diff --git a/gem/interpreter.py b/gem/interpreter.py
index a7e2e724..a95c3d9b 100644
--- a/gem/interpreter.py
+++ b/gem/interpreter.py
@@ -60,7 +60,7 @@ def filter(self, idx, fids):
         return tuple(idx[fids.index(i)] for i in self.fids) + idx[len(fids):]
 
     def __getitem__(self, idx):
-        return self.arr[idx]
+        return self.arr[tuple(idx)]
 
     def __setitem__(self, idx, val):
         self.arr[idx] = val
diff --git a/tsfc/tensor.py b/tsfc/tensor.py
index d4f80fa0..8902b470 100644
--- a/tsfc/tensor.py
+++ b/tsfc/tensor.py
@@ -31,7 +31,7 @@ def einsum(factors, sum_indices):
             else:
                 selectors.append(slice(None))
                 letters.append(index2letter[index])
-        operands.append(literal.array.__getitem__(selectors))
+        operands.append(literal.array.__getitem__(tuple(selectors)))
         subscript_parts.append(''.join(letters))
 
     result_pairs = sorted((letter, index)