diff --git a/kwave/kgrid.py b/kwave/kgrid.py
index 3476c7ab..666074e4 100644
--- a/kwave/kgrid.py
+++ b/kwave/kgrid.py
@@ -108,7 +108,7 @@ def t_array(self):
     @t_array.setter
     def t_array(self, t_array):
         # check for 'auto' input
-        if t_array == "auto":
+        if isinstance(t_array, str) and t_array == "auto":
             # set values to auto
             self.Nt = "auto"
             self.dt = "auto"