diff --git a/interfaces/cython/cantera/test/test_onedim.py b/interfaces/cython/cantera/test/test_onedim.py
index 7acc46f45..2690f0c59 100644
--- a/interfaces/cython/cantera/test/test_onedim.py
+++ b/interfaces/cython/cantera/test/test_onedim.py
@@ -961,7 +961,7 @@ class TestIonFreeFlame(utilities.CanteraTest):
         self.sim.solve(loglevel=0, stage=2, enable_energy=True)
 
         # Regression test
-        self.assertNear(max(self.sim.E), 136.1234, 1e-3)
+        self.assertNear(max(self.sim.E), 142.2677, 1e-3)
 
 
 class TestIonBurnerFlame(utilities.CanteraTest):
@@ -986,4 +986,4 @@ class TestIonBurnerFlame(utilities.CanteraTest):
         self.sim.solve(loglevel=0, stage=2, enable_energy=True)
 
         # Regression test
-        self.assertNear(max(self.sim.E), 539.59, 1e-2)
+        self.assertNear(max(self.sim.E), 552.33, 1e-2)
diff --git a/src/transport/IonGasTransport.cpp b/src/transport/IonGasTransport.cpp
index feba6809f..0acd9b397 100644
--- a/src/transport/IonGasTransport.cpp
+++ b/src/transport/IonGasTransport.cpp
@@ -355,6 +355,13 @@ void IonGasTransport::getMixDiffCoeffs(double* const d)
 
 void IonGasTransport::getMobilities(double* const mobi)
 {
+    update_T();
+    update_C();
+
+    // update the binary diffusion coefficients if necessary
+    if (!m_bindiff_ok) {
+        updateDiff_T();
+    }
     double p = m_thermo->pressure();
     for (size_t k = 0; k < m_nsp; k++) {
         if (k == m_kElectron) {