diff --git a/Lib/idlelib/EditorWindow.py b/Lib/idlelib/EditorWindow.py
index 38ae7b60aa4..cee7767d3b5 100644
--- a/Lib/idlelib/EditorWindow.py
+++ b/Lib/idlelib/EditorWindow.py
@@ -107,10 +107,18 @@ class EditorWindow(object):
         self.text_frame = text_frame = Frame(top)
         self.vbar = vbar = Scrollbar(text_frame, name='vbar')
         self.width = idleConf.GetOption('main','EditorWindow','width')
-        self.text = text = MultiCallCreator(Text)(
-                text_frame, name='text', padx=5, wrap='none',
-                width=self.width,
-                height=idleConf.GetOption('main','EditorWindow','height') )
+        text_options = {
+                'name': 'text',
+                'padx': 5,
+                'wrap': 'none',
+                'width': self.width,
+                'height': idleConf.GetOption('main', 'EditorWindow', 'height')}
+        if TkVersion >= 8.5:
+            # Starting with tk 8.5 we have to set the new tabstyle option
+            # to 'wordprocessor' to achieve the same display of tabs as in
+            # older tk versions.
+            text_options['tabstyle'] = 'wordprocessor'
+        self.text = text = MultiCallCreator(Text)(text_frame, **text_options)
         self.top.focused_widget = self.text
 
         self.createmenubar()
diff --git a/Lib/idlelib/NEWS.txt b/Lib/idlelib/NEWS.txt
index 87acd5f447e..c76174e0314 100644
--- a/Lib/idlelib/NEWS.txt
+++ b/Lib/idlelib/NEWS.txt
@@ -6,6 +6,9 @@ What's New in IDLE 3.1a1?
 - Remove port spec from run.py and fix bug where subprocess fails to
   extract port from command line when warnings are present.
 
+- Tk 8.5 Text widget requires 'wordprocessor' tabstyle attr to handle
+  mixed space/tab properly. Issue 5120, patch by Guilherme Polo.
+
 - Issue #4815: Offer conversion to UTF-8 if source files have
   no encoding declaration and are not encoded in UTF-8.