diff --git a/artiq/gui/experiments.py b/artiq/gui/experiments.py
index 9f1cfe9a4..424852c95 100644
--- a/artiq/gui/experiments.py
+++ b/artiq/gui/experiments.py
@@ -113,6 +113,7 @@ class _ArgumentEditor(QtWidgets.QTreeWidget):
         except:
             logger.error("Could not recompute argument '%s' of '%s'",
                          name, self.expurl, exc_info=True)
+            return
         argument = self.manager.get_submission_arguments(self.expurl)[name]
 
         procdesc = arginfo[name][0]