diff --git a/glue_ar/export_dialog.ui b/glue_ar/export_dialog.ui
index 5862f27..b382746 100644
--- a/glue_ar/export_dialog.ui
+++ b/glue_ar/export_dialog.ui
@@ -42,6 +42,9 @@
         <property name="text">
          <string>Cancel</string>
         </property>
+        <property name="autoDefault">
+         <bool>false</bool>
+        </property>
        </widget>
       </item>
       <item>
@@ -49,6 +52,9 @@
         <property name="text">
          <string>Export</string>
         </property>
+        <property name="autoDefault">
+         <bool>true</bool>
+        </property>
        </widget>
       </item>
      </layout>
diff --git a/glue_ar/volume.py b/glue_ar/volume.py
index 937ce2e..532167b 100644
--- a/glue_ar/volume.py
+++ b/glue_ar/volume.py
@@ -57,7 +57,7 @@ def meshes_for_volume_layer(viewer_state, layer_state, bounds,
     isodata = grid.contour([isomin])
 
     if smoothing_iterations > 0:
-        isodata = isodata.smooth(n_iter=smoothing_iterations)
+        isodata = isodata.smooth(n_iter=int(smoothing_iterations))
 
     return {
         "data": isodata,