diff --git a/python/oxford_asl/gui/cmdline.py b/python/oxford_asl/gui/cmdline.py
index e6ccf3f..40aead4 100644
--- a/python/oxford_asl/gui/cmdline.py
+++ b/python/oxford_asl/gui/cmdline.py
@@ -88,7 +88,10 @@ def add_arg(self, key, value=None):
             # Filenames might contain spaces so quote them
             if " " in value:
                 value = '"%s"' % value
-            self.cmd += " %s=%s" % (key, str(value))
+            if key.startswith('--'):
+                self.cmd += " %s=%s" % (key, str(value))
+            else:
+                self.cmd += ' %s %s' % (key, str(value))
         else:
             self.cmd += " %s" % key