diff --git a/interfaces/cython/cantera/ctml_writer.py b/interfaces/cython/cantera/ctml_writer.py
index de1809607..da546e9f2 100644
--- a/interfaces/cython/cantera/ctml_writer.py
+++ b/interfaces/cython/cantera/ctml_writer.py
@@ -845,11 +845,11 @@ class pureFluidParameters(activityCoefficients):
     def build(self,a):
         f= a.addChild("pureFluidParameters")
         f['species'] = self._species
-        s = '%10.4E, %10.4E \n' % (self._acoeff[0], self._acoeff[1])
+        s = '%.10g, %.10g\n' % (self._acoeff[0], self._acoeff[1])
         ac = f.addChild("a_coeff",s)
         ac["units"] = _upres+'-'+_ulen+'6/'+_umol+'2'
         ac["model"] = "linear_a"
-        s = '%0.2f \n' % self._bcoeff
+        s = '%.10g\n' % self._bcoeff
         bc = f.addChild("b_coeff",s)
         bc["units"] = _ulen+'3/'+_umol
 
@@ -864,12 +864,12 @@ class crossFluidParameters(activityCoefficients):
         f= a.addChild("crossFluidParameters")
         f["species2"] = self._species2
         f["species1"] = self._species1
-        s = '%10.4E, %10.4E \n' % (self._acoeff[0], self._acoeff[1])
+        s = '%.10g, %.10g\n' % (self._acoeff[0], self._acoeff[1])
         ac = f.addChild("a_coeff",s)
         ac["units"] = _upres+'-'+_ulen+'6/'+_umol+'2'
         ac["model"] = "linear_a"
         if self._bcoeff:
-            s = '%0.2f \n' % self._bcoeff
+            s = '%.10g\n' % self._bcoeff
             bc = f.addChild("b_coeff",s)
             bc["units"] = _ulen+'3/'+_umol
 
diff --git a/test/thermo/RedlichKwongMFTP_Test.cpp b/test/thermo/RedlichKwongMFTP_Test.cpp
index 3b26c62bf..75c88c41b 100644
--- a/test/thermo/RedlichKwongMFTP_Test.cpp
+++ b/test/thermo/RedlichKwongMFTP_Test.cpp
@@ -38,15 +38,15 @@ TEST_F(RedlichKwongMFTP_Test, chem_potentials)
     // where gamma_k is the activity coefficient.  Run regression test against values calculated using
     // the model.
     const double expected_result[9] = {
-        -4.573578067074649e+008,
-        -4.573471163377696e+008,
-        -4.573375748803425e+008,
-        -4.573290065058332e+008,
-        -4.573212695326964e+008,
-        -4.573142485189869e+008,
-        -4.573078484551440e+008,
-        -4.573019904340246e+008,
-        -4.572966083775078e+008
+        -4.573578072583122e+008,
+        -4.573471168532005e+008,
+        -4.573375753640399e+008,
+        -4.573290069609340e+008,
+        -4.573212699618942e+008,
+        -4.573142489246118e+008,
+        -4.573078488392255e+008,
+        -4.573019907983406e+008,
+        -4.572966087236250e+008
     };
 
     double xmin = 0.6;
@@ -125,30 +125,30 @@ TEST_F(RedlichKwongMFTP_Test, setTP)
 
     // All sub-cooled liquid:
     const double p1[6] = {
-        1.587029921158317e+002,
-        1.541895558698696e+002,
-        1.501572815648243e+002,
-        1.465106359800041e+002,
-        1.431807662747959e+002,
-        1.401162435728261e+002
+        1.587112190732014e+002,
+        1.541966713372675e+002,
+        1.501635359781652e+002,
+        1.465162036435630e+002,
+        1.431857735462774e+002,
+        1.401207850479111e+002
     };
     // Phase change between temperatures 4 & 5:
     const double p2[6] = {
-        6.265136821574670e+002,
-        5.991027079853330e+002,
-        5.656903533839055e+002,
-        5.196021189855490e+002,
-        3.384435863009947e+002,
-        2.755331531855265e+002
+        6.267097216456422e+002,
+        5.993217207540168e+002,
+        5.659501111117172e+002,
+        5.199644273242080e+002,
+        3.393007538579040e+002,
+        2.756259035569044e+002
     };
     // Supercritical; no discontinuity in rho values:
     const double p3[6] = {
-        6.839819449357851e+002,
-        6.667277456641792e+002,
-        6.483568057147166e+002,
-        6.286479753170340e+002,
-        6.073051275696215e+002,
-        5.839223896051005e+002
+        6.841288400828764e+002,
+        6.668789423328959e+002,
+        6.485130892980700e+002,
+        6.288103574172300e+002,
+        6.074749284756613e+002,
+        5.841013398471708e+002
     };
 
     for(int i=0; i<6; ++i)