diff --git a/eeschema/sim/sim_plot_panel.h b/eeschema/sim/sim_plot_panel.h
index 77873d64f5..75b12fb988 100644
--- a/eeschema/sim/sim_plot_panel.h
+++ b/eeschema/sim/sim_plot_panel.h
@@ -224,6 +224,9 @@ public:
 
     bool IsGridShown() const
     {
+        if( !m_axis_x || !m_axis_y1 )
+            return false;
+
         assert( m_axis_x->GetTicks() == m_axis_y1->GetTicks() );
         return !m_axis_x->GetTicks();
     }