diff --git a/src/calibre/gui2/markdown_syntax_highlighter.py b/src/calibre/gui2/markdown_syntax_highlighter.py
index 118365550e..b29311eeb2 100644
--- a/src/calibre/gui2/markdown_syntax_highlighter.py
+++ b/src/calibre/gui2/markdown_syntax_highlighter.py
@@ -16,21 +16,21 @@ class MarkdownHighlighter(QSyntaxHighlighter):
     MARKDOWN_KEYS_REGEX = {
         'Bold' : re.compile(r'(?P<delim>\*\*)(?P<text>.+)(?P=delim)'),
         'uBold': re.compile('(?P<delim>__)(?P<text>[^_]{2,})(?P=delim)'),
-        'Italic': re.compile('(?P<delim>\*)(?P<text>[^*]{2,})(?P=delim)'),
+        'Italic': re.compile(r'(?P<delim>\*)(?P<text>[^*]{2,})(?P=delim)'),
         'uItalic': re.compile('(?P<delim>_)(?P<text>[^_]+)(?P=delim)'),
         'Link': re.compile('(?u)(^|(?P<pre>[^!]))\[.*?\]:?[ \t]*\(?[^)]+\)?'),
-        'Image': re.compile('(?u)!\[.*?\]\(.+?\)'),
-        'HeaderAtx': re.compile('(?u)^\#{1,6}(.*?)\#*(\n|$)'),
+        'Image': re.compile(r'(?u)!\[.*?\]\(.+?\)'),
+        'HeaderAtx': re.compile(r'(?u)^\#{1,6}(.*?)\#*(''\n|$)'),
         'Header': re.compile('^(.+)[ \t]*\n(=+|-+)[ \t]*\n+'),
         'CodeBlock': re.compile('^([ ]{4,}|\t).*'),
-        'UnorderedList': re.compile('(?u)^\s*(\* |\+ |- )+\s*'),
-        'UnorderedListStar': re.compile('^\s*(\* )+\s*'),
-        'OrderedList': re.compile('(?u)^\s*(\d+\. )\s*'),
-        'BlockQuote': re.compile('(?u)^\s*>+\s*'),
+        'UnorderedList': re.compile(r'(?u)^\s*(\* |\+ |- )+\s*'),
+        'UnorderedListStar': re.compile(r'^\s*(\* )+\s*'),
+        'OrderedList': re.compile(r'(?u)^\s*(\d+\. )\s*'),
+        'BlockQuote': re.compile(r'(?u)^\s*>+\s*'),
         'BlockQuoteCount': re.compile('^[ \t]*>[ \t]?'),
         'CodeSpan': re.compile('(?P<delim>`+).+?(?P=delim)'),
-        'HR': re.compile('(?u)^(\s*(\*|-)\s*){3,}$'),
-        'eHR': re.compile('(?u)^(\s*(\*|=)\s*){3,}$'),
+        'HR': re.compile(r'(?u)^(\s*(\*|-)\s*){3,}$'),
+        'eHR': re.compile(r'(?u)^(\s*(\*|=)\s*){3,}$'),
         'Html': re.compile('<.+?>')
     }