diff --git a/joy/gui/textwidget.py b/joy/gui/textwidget.py
index 02defe8..9eea55b 100644
--- a/joy/gui/textwidget.py
+++ b/joy/gui/textwidget.py
@@ -297,6 +297,7 @@ class TextViewerWidget(tk.Text, MouseBindingsMixin, SavingMixin):
 
   def run_command(self, command):
     '''Given a string run it on the stack, report errors.'''
+    command = command.encode('utf_8')
     try:
       self.world.interpret(command)
     except SystemExit: