diff --git a/src/calibre/ebooks/metadata/sources/update.py b/src/calibre/ebooks/metadata/sources/update.py
index 7ef06e6ecc..52355c52af 100644
--- a/src/calibre/ebooks/metadata/sources/update.py
+++ b/src/calibre/ebooks/metadata/sources/update.py
@@ -57,6 +57,8 @@ def update_plugin(name):
 
 def main(report_error, report_action=prints):
     try:
+        if time.time() - cache.mtime() < UPDATE_INTERVAL:
+            return
         try:
             report_action('Fetching metadata source hashes...')
             needed = update_needed()
@@ -78,9 +80,6 @@ def main(report_error, report_action=prints):
 def update_sources(wait_for_completion=False):
     if update_sources.worker is not None:
         return False
-    epoch = cache.get('last_update', 0)
-    if time.time() - epoch < UPDATE_INTERVAL:
-        return False
     update_sources.errors = errs = []
     update_sources.worker = t = Thread(
         target=main, args=(errs.append, debug_print), name='MSourcesUpdater')
diff --git a/src/calibre/utils/config.py b/src/calibre/utils/config.py
index 4463ec5f31..ce69cd56c8 100644
--- a/src/calibre/utils/config.py
+++ b/src/calibre/utils/config.py
@@ -286,6 +286,12 @@ class XMLConfig(dict):
 
         self.refresh()
 
+    def mtime(self):
+        try:
+            return os.path.getmtime(self.file_path)
+        except EnvironmentError:
+            return 0
+
     def raw_to_object(self, raw):
         return plistlib.readPlistFromString(raw)