diff --git a/mkdocs/config/config_options.py b/mkdocs/config/config_options.py
index aa0a9727..e0e91fd5 100644
--- a/mkdocs/config/config_options.py
+++ b/mkdocs/config/config_options.py
@@ -293,7 +293,17 @@ class Theme(OptionallyRequired):
         themes = utils.get_theme_names()
 
         if value in themes:
-            if value in ['mkdocs', 'readthedocs']:
+
+            # These themes have been moved to the mkdocs-bootstrap and
+            # mkdocs-bootswatch packages. At some point we wont depend on
+            # these by default.
+            moved_themes = [
+                'bootstrap', 'amelia', 'cerulean', 'cosmo', 'cyborg',
+                'flatly', 'journal', 'readable', 'simplex', 'slate',
+                'spacelab', 'united', 'yeti'
+            ]
+
+            if value not in moved_themes:
                 return value
 
             self.warnings.append(