diff --git a/interfaces/cython/cantera/ck2cti.py b/interfaces/cython/cantera/ck2cti.py
index 92ab9c045..0e52b91b6 100644
--- a/interfaces/cython/cantera/ck2cti.py
+++ b/interfaces/cython/cantera/ck2cti.py
@@ -70,16 +70,17 @@ if sys.version_info[0] == 2:
     def strip_nonascii(s):
         return s.decode('ascii', 'ignore')
 
-    def open(filename, *args):
-        return _open(filename, *args)
+    def open(filename, mode, *args):
+        return _open(filename, mode, *args)
 
 else:
     string_types = (str,)
     def strip_nonascii(s):
         return s.encode('ascii', 'ignore').decode()
 
-    def open(filename, *args):
-        return _open(filename, *args, errors='ignore')
+    def open(filename, mode, *args):
+        mode = mode.replace('U', '')
+        return _open(filename, mode, *args, errors='ignore')
 
 
 def compatible_quantities(quantity_basis, units):
diff --git a/interfaces/cython/cantera/test/test_onedim.py b/interfaces/cython/cantera/test/test_onedim.py
index 2a3b2110b..6480cdfc9 100644
--- a/interfaces/cython/cantera/test/test_onedim.py
+++ b/interfaces/cython/cantera/test/test_onedim.py
@@ -360,7 +360,7 @@ class TestFreeFlame(utilities.CanteraTest):
 
         self.create_sim(2e5, 350, 'H2:1.0, O2:2.0', mech='h2o2.xml')
         self.sim.write_csv(filename)
-        data = np.genfromtxt(filename, delimiter=',', skiprows=1)
+        data = np.genfromtxt(filename, delimiter=',', skip_header=1)
         self.assertArrayNear(data[:,0], self.sim.grid)
         self.assertArrayNear(data[:,3], self.sim.T)
         k = self.gas.species_index('H2')