Index: Lib/tkinter/test/test_ttk/test_widgets.py
===================================================================
--- Lib/tkinter/test/test_ttk/test_widgets.py	(revision 88757)
+++ Lib/tkinter/test/test_ttk/test_widgets.py	(working copy)
@@ -188,6 +188,10 @@
         self.combo.configure(values=[1, '', 2])
         self.assertEqual(self.combo['values'], ('1', '', '2'))
 
+        # testing values with spaces or \
+        self.combo['values'] = ['a b', r'a\tb']
+        self.assertEqual(self.combo['values'], ('a b', r'a\tb'))
+
         # out of range
         self.assertRaises(tkinter.TclError, self.combo.current,
             len(self.combo['values']))
Index: Lib/tkinter/ttk.py
===================================================================
--- Lib/tkinter/ttk.py	(revision 88757)
+++ Lib/tkinter/ttk.py	(working copy)
@@ -47,6 +47,9 @@
         master.tk.eval('package require tile') # TclError may be raised here
         master._tile_loaded = True
 
+def _need_braces(value):
+    return ' ' in value or '\\' in value
+
 def _format_optdict(optdict, script=False, ignore=None):
     """Formats optdict to a tuple to pass it to tk.call.
 
@@ -71,7 +74,7 @@
             # format v according to the script option, but also check for
             # space in any value in v in order to group them correctly
             value = format % ' '.join(
-                ('{%s}' if ' ' in val else '%s') % val for val in v)
+                ('{%s}' if _need_braces(val) else '%s') % val for val in v)
 
         if script and value == '':
             value = '{}' # empty string in Python is equivalent to {} in Tcl