--- a/QScintilla/Shell.py	Fri Dec 13 22:45:47 2013 +0100
+++ b/QScintilla/Shell.py	Fri Dec 13 23:39:14 2013 +0100
@@ -428,8 +428,9 @@
         @param on flag to indicate usage of a monospace font (boolean)
         """
         if on:
-            f = Preferences.getShell("MonospacedFont")
-            self.monospacedStyles(f)
+            if not self.lexer_:
+                f = Preferences.getShell("MonospacedFont")
+                self.monospacedStyles(f)
         else:
             if not self.lexer_:
                 self.clearStyles()