diff --git a/ubuntutools/config.py b/ubuntutools/config.py
index d0e2409..1235e59 100644
--- a/ubuntutools/config.py
+++ b/ubuntutools/config.py
@@ -98,9 +98,12 @@ class UDTConfig(object):
                         else:
                             continue
                     if k in compat_keys:
+                        r_prefix = self.prefix
+                        if key in self.defaults:
+                            r_prefix = 'UBUNTUTOOLS'
                         print >> stderr, (
                                 'W: Deprecated configuration variable: %s. '
-                                'Replaced by %s.') % (k, key)
+                                'Replaced by %s_%s.') % (k, r_prefix, key)
                     return value
         return default
 
diff --git a/ubuntutools/test/test_config.py b/ubuntutools/test/test_config.py
index 992edd4..8606830 100644
--- a/ubuntutools/test/test_config.py
+++ b/ubuntutools/test/test_config.py
@@ -128,7 +128,8 @@ REPEAT=yes
         errs = ubuntutools.config.stderr.getvalue().strip()
         ubuntutools.config.stderr = StringIO()
         self.assertEqual(len(errs.splitlines()), 1)
-        self.assertRegexpMatches(errs, r'Deprecated.*\bCOMPATFOOBAR\b.*\bQUX\b')
+        self.assertRegexpMatches(errs,
+                r'Deprecated.*\bCOMPATFOOBAR\b.*\bTEST_QUX\b')
 
     def test_boolean(self):
         config_files['user'] = "TEST_BOOLEAN=yes"