diff --git a/interfaces/cython/cantera/ctml_writer.py b/interfaces/cython/cantera/ctml_writer.py
index f2f908f44e5..8ad99db4de0 100644
--- a/interfaces/cython/cantera/ctml_writer.py
+++ b/interfaces/cython/cantera/ctml_writer.py
@@ -1138,11 +1138,10 @@ def __init__(self,
         if self._order:
             order = getPairs(self._order)
             for o in order.keys():
-                if o in self._rxnorder:
-                    self._rxnorder[o] = order[o]
+                if o not in self._rxnorder and 'nonreactant_orders' not in self._options:
+                    raise CTI_Error("order specified for non-reactant: "+o+" and no \'nonreactant_orders\' option given")
                 else:
-                    if 'nonreactant_orders' not in self._options:
-                        raise CTI_Error("order specified for non-reactant: "+o)
+                    self._rxnorder[o] = order[o]
 
         self._kf = kf
         self._igspecies = []
diff --git a/interfaces/cython/cantera/test/test_convert.py b/interfaces/cython/cantera/test/test_convert.py
index be9c4d88d20..4ee62fe1b0e 100644
--- a/interfaces/cython/cantera/test/test_convert.py
+++ b/interfaces/cython/cantera/test/test_convert.py
@@ -390,3 +390,13 @@ def test_noninteger_atomicity(self):
         gas = ct.Solution('../data/noninteger-atomicity.cti')
         self.assertNear(gas.molecular_weights[gas.species_index('CnHm')],
                         10.65*gas.atomic_weight('C') + 21.8*gas.atomic_weight('H'))
+
+    def test_reaction_orders(self):
+        gas = ct.Solution('../data/non-reactant-species.cti')
+        R=gas.reaction(0)
+        allow=R.allow_nonreactant_orders
+        self.assertEqual(allow, True)
+        self.assertNear(R.orders.get('OH'), 0.15)
+        allow=R.allow_negative_orders
+        self.assertEqual(allow, True)
+        self.assertNear(R.orders.get('H2'), -0.25)
diff --git a/test/data/reaction-orders.cti b/test/data/reaction-orders.cti
new file mode 100644
index 00000000000..77d3c8a2e1b
--- /dev/null
+++ b/test/data/reaction-orders.cti
@@ -0,0 +1,23 @@
+# Input file to test use of non-reactant species
+
+units(length = "cm", time = "s", quantity = "mol", act_energy = "kJ/mol")
+
+ideal_gas(name = "gas",
+      elements = " O H ",
+      species = """gri30: H2  O2  H2O OH """,
+      reactions = "all",
+      initial_state = state(temperature = 300.0,
+                        pressure = OneAtm)    )
+
+#-------------------------------------------------------------------------------
+#  Reactions data
+#-------------------------------------------------------------------------------
+
+#test negative orders and non-reactant orders
+reaction("2 H2 + O2 => 2 H2O", [1e13, 0.0, 0.0],
+         order="H2:-0.25 OH:0.15", 
+         options=['negative_orders', 'nonreactant_orders'])
+
+#if uncomment, should throw an error
+#reaction("2 H2 + O2 => 2 H2O", [1e13, 0.0, 0.0],
+#         order="OH:0.15")