diff --git a/src/calibre/gui2/viewer/search.py b/src/calibre/gui2/viewer/search.py
index 8ae7dcb924..fcb4fa9baa 100644
--- a/src/calibre/gui2/viewer/search.py
+++ b/src/calibre/gui2/viewer/search.py
@@ -54,7 +54,7 @@ def stop(self):
 quote_map= {'"':'"“”', "'": "'‘’"}
 qpat = regex.compile(r'''(['"])''')
 spat = regex.compile(r'(\s+)')
-invisible_chars = '(?:[\u00ad\u200d]{0,1})'
+invisible_chars = '(?:[\u00ad\u200c\u200d]{0,1})'
 
 
 def text_to_regex(text):