diff --git a/src/calibre/ebooks/metadata/rtf.py b/src/calibre/ebooks/metadata/rtf.py
index b888f81844..1d629c50d0 100644
--- a/src/calibre/ebooks/metadata/rtf.py
+++ b/src/calibre/ebooks/metadata/rtf.py
@@ -206,7 +206,7 @@ def set_metadata(stream, options):
         def replace_or_create(src, name, val):
             val = encode(val)
             pat = re.compile(base_pat.replace('name', name), re.DOTALL)
-            src, num = pat.subn('{\\' + name + ' ' + val + '}', src)
+            src, num = pat.subn(r'{\\' + name + ' ' + val + '}', src)
             if num == 0:
                 src = add_metadata_item(src, name, val)
             return src