diff --git a/src/petab_gui/views/simple_plot_view.py b/src/petab_gui/views/simple_plot_view.py
index eb11514..b9c0b59 100644
--- a/src/petab_gui/views/simple_plot_view.py
+++ b/src/petab_gui/views/simple_plot_view.py
@@ -180,7 +180,7 @@ def _render_on_main_thread(self, payload):
             meas_df is None
             or meas_df.empty
             or cond_df is None
-            or cond_df.empty
+            or not len(cond_df) > 0
         ):
             self._update_tabs(None)
             return