--- a/eric6/E5Gui/E5MainWindow.py	Tue Oct 13 19:02:26 2020 +0200
+++ b/eric6/E5Gui/E5MainWindow.py	Wed Oct 14 17:50:39 2020 +0200
@@ -48,9 +48,8 @@
         # step 2: set a style sheet
         if styleSheetFile:
             try:
-                f = open(styleSheetFile, "r", encoding="utf-8")
-                styleSheet = f.read()
-                f.close()
+                with open(styleSheetFile, "r", encoding="utf-8") as f:
+                    styleSheet = f.read()
             except (IOError, OSError) as msg:
                 E5MessageBox.warning(
                     self,