diff --git a/pyop/block.py b/pyop/block.py
index af02331..31d4e9b 100644
--- a/pyop/block.py
+++ b/pyop/block.py
@@ -190,8 +190,8 @@ def forwardFunction(x):
 
         ## Apply each operator to corresponding subvector and concatenate
         ## the results.
-        sub_outvecs = (b(v) for (b, v) in six.moves.zip(blocks,
-            vec_components))
+        sub_outvecs = [b(v) for (b, v) in six.moves.zip(blocks,
+            vec_components)]
 
         ## Concatenate the output sub-vectors together.
         return npvstack(sub_outvecs)
@@ -206,8 +206,8 @@ def adjointFunction(x):
 
         ## Apply each operator to corresponding subvector and concatenate
         ## the results.
-        sub_outvecs = (b.T(v) for (b, v) in six.moves.zip(blocks,
-            vec_components))
+        sub_outvecs = [b.T(v) for (b, v) in six.moves.zip(blocks,
+            vec_components)]
 
         ## Concatenate the output sub-vectors together.
         return npvstack(sub_outvecs)
@@ -252,7 +252,7 @@ def opFunction(x):
 
         ## Apply each operator (forward or adjoint) to the input vector to
         ## get output vector sub-components.
-        sub_outvecs = (b(x) for b in vert_blocks)
+        sub_outvecs = [b(x) for b in vert_blocks]
         ## Concatenate the output sub-vectors together.
         return npvstack(sub_outvecs)
 
diff --git a/pyop/convert.py b/pyop/convert.py
index e910c86..b660d33 100644
--- a/pyop/convert.py
+++ b/pyop/convert.py
@@ -112,7 +112,7 @@ def toMatrix(O, sparse = False):
 #  Scipy  #
 ###########
 
-def toScipyLinearOperator(O, dtype = np.float):
+def toScipyLinearOperator(O, dtype = np.float64):
     ''' Converts a LinearOperator into a scipy.sparse.linalg.LinearOperator
 
     Scipy comes with come handy functions for calculating properties of a
diff --git a/pyop/utilities.py b/pyop/utilities.py
index c361ce0..c1bed5b 100644
--- a/pyop/utilities.py
+++ b/pyop/utilities.py
@@ -134,7 +134,7 @@ def matvec(f):
 
     @matmat
     def wrapper(x):
-        return np.column_stack(f(c) for c in x.T)
+        return np.column_stack([f(c) for c in x.T])
 
     return __wrapIfPy3(wrapper, f)
 
diff --git a/tests/convert_test.py b/tests/convert_test.py
index 522ea58..d8c9025 100644
--- a/tests/convert_test.py
+++ b/tests/convert_test.py
@@ -74,4 +74,4 @@ def testToScipyLinearOperator():
 
         np.testing.assert_allclose(A_op(input_mat), A_sci(input_mat))
         np.testing.assert_allclose(A_op.T(input_mat),
-                                   A_sci.rmatvec(input_mat))
+                                   A_sci.rmatmat(input_mat))