diff --git a/src/calibre/ebooks/conversion/preprocess.py b/src/calibre/ebooks/conversion/preprocess.py
index 72032cb998..82cc4c0f4a 100644
--- a/src/calibre/ebooks/conversion/preprocess.py
+++ b/src/calibre/ebooks/conversion/preprocess.py
@@ -515,6 +515,7 @@ class HTMLPreProcessor(object):
         if not getattr(self.extra_opts, 'keep_ligatures', False):
             html = _ligpat.sub(lambda m:LIGATURES[m.group()], html)
 
+        user_sr_rules = {}
         # Function for processing search and replace
         def do_search_replace(search_pattern, replace_txt):
             try:
@@ -522,6 +523,7 @@ class HTMLPreProcessor(object):
                 if not replace_txt:
                     replace_txt = ''
                 rules.insert(0, (search_re, replace_txt))
+                user_sr_rules[(search_re, replace_txt)] = search_pattern
             except Exception as e:
                 self.log.error('Failed to parse %r regexp because %s' %
                         (search, as_unicode(e)))
@@ -587,7 +589,16 @@ class HTMLPreProcessor(object):
         #dump(html, 'pre-preprocess')
 
         for rule in rules + end_rules:
-            html = rule[0].sub(rule[1], html)
+            try:
+                html = rule[0].sub(rule[1], html)
+            except re.error as e:
+                if rule in user_sr_rules:
+                    self.log.error(
+                        'User supplied search & replace rule: %s -> %s '
+                        'failed with error: %s, ignoring.'%(
+                            user_sr_rules[rule], rule[1], e))
+                else:
+                    raise
 
         if is_pdftohtml and length > -1:
             # Dehyphenate