diff --git a/ks_includes/widgets/heatergraph.py b/ks_includes/widgets/heatergraph.py
index eda5eefb..cf44a44a 100644
--- a/ks_includes/widgets/heatergraph.py
+++ b/ks_includes/widgets/heatergraph.py
@@ -44,7 +44,8 @@ class HeaterGraph(Gtk.DrawingArea):
 
     def get_max_length(self):
         return min(len(self.printer.get_temp_store(name, "temperatures"))
-                   for name in self.store if "temperatures" in self.store[name])
+                   for name in self.store if "temperatures" in self.store[name]
+                   and self.printer.get_temp_store(name, "temperatures"))
 
     def get_max_num(self, data_points=0):
         mnum = [0]