diff --git a/src/calibre/ebooks/conversion/__init__.py b/src/calibre/ebooks/conversion/__init__.py
index e9461c7279..86b581992f 100644
--- a/src/calibre/ebooks/conversion/__init__.py
+++ b/src/calibre/ebooks/conversion/__init__.py
@@ -23,3 +23,6 @@ class ConversionUserFeedBack(Exception):
         self.title, self.msg, self.det_msg = title, msg, det_msg
         self.level = level
 
+# Ensure exception uses fully qualified name as this is used to detect it in
+# the GUI.
+ConversionUserFeedBack.__name__ = str('calibre.ebooks.conversion.ConversionUserFeedBack')