diff --git a/energyplus_regressions/tk_window.py b/energyplus_regressions/tk_window.py
index 2daeb7d..5019fff 100644
--- a/energyplus_regressions/tk_window.py
+++ b/energyplus_regressions/tk_window.py
@@ -149,7 +149,7 @@ def __init__(self):
             else:
                 print(f"Could not set icon for Mac, expecting to find it at {self.icon_path}")
         elif system() == 'Windows':
-            self.icon_path = Path(__file__).resolve().parent / 'icons' / 'icon.ico'
+            self.icon_path = Path(__file__).resolve().parent / 'icons' / 'icon.png'
             img = PhotoImage(file=str(self.icon_path))
             if self.icon_path.exists():
                 self.root.iconphoto(False, img)