diff -r 17efda0a2b2b Lib/idlelib/configDialog.py
--- a/Lib/idlelib/configDialog.py	Sat May 19 21:25:41 2012 +0000
+++ b/Lib/idlelib/configDialog.py	Tue May 22 06:32:18 2012 -0500
@@ -187,7 +187,7 @@
                               text=' Highlighting Theme ')
         #frameCustom
         self.textHighlightSample=Text(frameCustom,relief=SOLID,borderwidth=1,
-            font=('courier',12,''),cursor='hand2',width=21,height=10,
+            font=('courier',12,''),cursor='hand2',width=21,height=11,
             takefocus=FALSE,highlightthickness=0,wrap=NONE)
         text=self.textHighlightSample
         text.bind('<Double-Button-1>',lambda e: 'break')
@@ -821,8 +821,10 @@
             fontWeight=tkFont.BOLD
         else:
             fontWeight=tkFont.NORMAL
-        self.editFont.config(size=self.fontSize.get(),
+        size=self.fontSize.get()
+        self.editFont.config(size=size,
                 weight=fontWeight,family=fontName)
+        self.textHighlightSample.configure(font=(fontName, size, fontWeight))
 
     def SetHighlightTarget(self):
         if self.highlightTarget.get()=='Cursor': #bg not possible