diff --git a/manual/custom.py b/manual/custom.py
index 324176b7a1..9de4c4f60f 100644
--- a/manual/custom.py
+++ b/manual/custom.py
@@ -236,8 +236,7 @@ def render_options(cmd, groups, options_header=True, add_program=True, header_le
 
 
 def mark_options(raw):
-    if 'CALIBRE_BUILD_MAN_PAGES' not in os.environ:
-        raw = re.sub(r'(\s+)--(\s+)', ur'\1-\N{ZERO WIDTH SPACE}-\2', raw)
+    raw = re.sub(r'(\s+)--(\s+)', ur'\1``--``\2', raw)
 
     def sub(m):
         opt = m.group()