diff --git a/endurance_line_shading.py b/endurance_line_shading.py
index 1e05e38..b339689 100644
--- a/endurance_line_shading.py
+++ b/endurance_line_shading.py
@@ -310,7 +310,7 @@ def export_png(self, node, file):
       image_w = float(node.get('width'))
       image_h = float(node.get('height'))
       min_period = self.options.min_period 
-      max_period = self.options.min_period        
+      max_period = self.options.max_period
       poinnt_per_min_period = 8.0           
       current_file = self.args[-1]
       h_png = str(self.options.num_lines)