diff --git a/src/calibre/ebooks/conversion/utils.py b/src/calibre/ebooks/conversion/utils.py
index 95f832c76a..2e26f927f5 100644
--- a/src/calibre/ebooks/conversion/utils.py
+++ b/src/calibre/ebooks/conversion/utils.py
@@ -156,17 +156,17 @@ class HeuristicProcessor(object):
         ]
 
         ITALICIZE_STYLE_PATS = [
-            r'(?msu)(?<=[\s>])_(?P<words>[^_]+)?_',
-            r'(?msu)(?<=[\s>])/(?P<words>[^/]+)?/',
-            r'(?msu)(?<=[\s>])~~(?P<words>[^~]+)?~~',
-            r'(?msu)(?<=[\s>])\*(?P<words>[^\*]+)?\*',
-            r'(?msu)(?<=[\s>])~(?P<words>[^~]+)?~',
-            r'(?msu)(?<=[\s>])_/(?P<words>[^/_]+)?/_',
-            r'(?msu)(?<=[\s>])_\*(?P<words>[^\*_]+)?\*_',
-            r'(?msu)(?<=[\s>])\*/(?P<words>[^/\*]+)?/\*',
-            r'(?msu)(?<=[\s>])_\*/(?P<words>[^\*_]+)?/\*_',
-            r'(?msu)(?<=[\s>])/:(?P<words>[^:/]+)?:/',
-            r'(?msu)(?<=[\s>])\|:(?P<words>[^:\|]+)?:\|',
+            r'(?msu)(?<=[\s>])_(?P<words>[^_]+)_',
+            r'(?msu)(?<=[\s>])/(?P<words>[^/]+)/',
+            r'(?msu)(?<=[\s>])~~(?P<words>[^~]+)~~',
+            r'(?msu)(?<=[\s>])\*(?P<words>[^\*]+)\*',
+            r'(?msu)(?<=[\s>])~(?P<words>[^~]+)~',
+            r'(?msu)(?<=[\s>])_/(?P<words>[^/_]+)/_',
+            r'(?msu)(?<=[\s>])_\*(?P<words>[^\*_]+)\*_',
+            r'(?msu)(?<=[\s>])\*/(?P<words>[^/\*]+)/\*',
+            r'(?msu)(?<=[\s>])_\*/(?P<words>[^\*_]+)/\*_',
+            r'(?msu)(?<=[\s>])/:(?P<words>[^:/]+):/',
+            r'(?msu)(?<=[\s>])\|:(?P<words>[^:\|]+):\|',
         ]
 
         for word in ITALICIZE_WORDS: