diff --git a/interfaces/matlab/toolbox/@ThermoPhase/display.m b/interfaces/matlab/toolbox/@ThermoPhase/display.m
index c154b95e0..414fc6bc6 100644
--- a/interfaces/matlab/toolbox/@ThermoPhase/display.m
+++ b/interfaces/matlab/toolbox/@ThermoPhase/display.m
@@ -1,5 +1,5 @@
 function display(self, threshold)
-if nargin < 2
+if nargin < 2 || ~isnumeric(threshold)
     threshold = 1e-14;
 end
 phase_get(thermo_hndl(self), 15, 1, threshold);