diff --git a/interfaces/matlab/toolbox/1D/npflame_init.m b/interfaces/matlab/toolbox/1D/npflame_init.m
index 0d064afb4..ef54ea1af 100644
--- a/interfaces/matlab/toolbox/1D/npflame_init.m
+++ b/interfaces/matlab/toolbox/1D/npflame_init.m
@@ -91,7 +91,7 @@ teq = temperature(gas);
 yeq = massFractions(gas);
 
 % estimated strain rate
-zz = z(flow);
+zz = gridPoints(flow);
 dz = zz(end) - zz(1);
 vleft = massFlux(left)/rho0;
 vright = massFlux(right)/rho0;
diff --git a/samples/matlab/flame.m b/samples/matlab/flame.m
index 097527248..958625328 100644
--- a/samples/matlab/flame.m
+++ b/samples/matlab/flame.m
@@ -61,7 +61,7 @@ if flametype == 0
 else
   t1 = temperature(right);
 end
-zz = z(flow);
+zz = gridPoints(flow);
 dz = zz(end) - zz(1);
 setProfile(f, 2, {'u', 'V'}, [0.0            1.0
                               mdot0/rho0     -mdot1/rho0