diff --git a/src/calibre/customize/ui.py b/src/calibre/customize/ui.py
index 9b5eb17fb8..f8e4f17c07 100644
--- a/src/calibre/customize/ui.py
+++ b/src/calibre/customize/ui.py
@@ -21,9 +21,9 @@ from calibre.ebooks.metadata import MetaInformation
 from calibre.utils.config import (make_config_dir, Config, ConfigProxy,
                                  plugin_dir, OptionParser)
 from calibre.ebooks.metadata.sources.base import Source
-from calibre.constants import DEBUG
+from calibre.constants import DEBUG, numeric_version
 
-builtin_names = frozenset([p.name for p in builtin_plugins])
+builtin_names = frozenset(p.name for p in builtin_plugins)
 
 
 class NameConflict(ValueError):
@@ -615,6 +615,18 @@ def all_metadata_plugins():
     for plugin in _initialized_plugins:
         if isinstance(plugin, Source):
             yield plugin
+
+
+def patch_metadata_plugins(possibly_updated_plugins):
+    patches = {}
+    for i, plugin in enumerate(_initialized_plugins):
+        if isinstance(plugin, Source) and plugin.name in builtin_names:
+            pup = possibly_updated_plugins.get(plugin.name)
+            if pup is not None:
+                if pup.version > plugin.version and pup.minimum_calibre_version <= numeric_version:
+                    patches[i] = pup
+    for i, pup in patches.iteritems():
+        _initialized_plugins[i] = pup
 # }}}
 
 # Viewer plugins {{{
diff --git a/src/calibre/ebooks/metadata/sources/update.py b/src/calibre/ebooks/metadata/sources/update.py
index a9e7c6a56b..2dd7737f7d 100644
--- a/src/calibre/ebooks/metadata/sources/update.py
+++ b/src/calibre/ebooks/metadata/sources/update.py
@@ -13,6 +13,8 @@ from threading import Thread
 
 from calibre import as_unicode, prints
 from calibre.constants import DEBUG
+from calibre.customize.ui import patch_metadata_plugins
+from calibre.ebooks.metadata.sources.base import Source
 from calibre.utils.config import JSONConfig
 from calibre.utils.https import get_https_resource_securely
 
@@ -26,6 +28,25 @@ def debug_print(*args, **k):
         prints(*args, **k)
 
 
+def load_plugin(src):
+    src = src.encode('utf-8')
+    ns = {}
+    exec src in ns
+    for x in ns.itervalues():
+        if isinstance(x, type) and issubclass(x, Source) and x is not Source:
+            return x
+
+
+def patch_plugins():
+    patches = {}
+    for name, val in cache.iteritems():
+        if name != 'hashes':
+            p = load_plugin(val)
+            if p is not None:
+                patches[p.name] = p
+    patch_metadata_plugins(patches)
+
+
 def update_needed():
     needed = set()
     current_hashes = cache.get('hashes', {})