diff --git a/src/calibre/constants.py b/src/calibre/constants.py
index 0029cb9a33..eced47ceaf 100644
--- a/src/calibre/constants.py
+++ b/src/calibre/constants.py
@@ -203,8 +203,10 @@ class DeVendor:
             return find_spec('feedparser')
         if fullname.startswith('calibre.ebooks.markdown'):
             return ModuleSpec(fullname, DeVendorLoader(fullname[len('calibre.ebooks.'):]))
-        if fullname.startswith('PyQt5.'):
+        if fullname.startswith('PyQt5'):
             # this is present for third party plugin compat
+            if fullname == 'PyQt5':
+                return ModuleSpec(fullname, DeVendorLoader('qt'))
             return ModuleSpec(fullname, DeVendorLoader('qt.webengine' if 'QWebEngine' in fullname else 'qt.core'))
         if fullname.startswith('Cryptodome'):
             # this is needed for py7zr which uses pycryptodomex instead of