diff --git a/src/calibre/ebooks/conversion/plugins/html_input.py b/src/calibre/ebooks/conversion/plugins/html_input.py
index a0624d98ac..0c30005b60 100644
--- a/src/calibre/ebooks/conversion/plugins/html_input.py
+++ b/src/calibre/ebooks/conversion/plugins/html_input.py
@@ -19,7 +19,7 @@ from calibre.utils.filenames import ascii_filename
 from calibre.utils.imghdr import what
 
 def sanitize_file_name(x):
-    return ascii_filename(x).replace(';', '_')
+    return re.sub(r'[?&=;]', '_', ascii_filename(x))
 
 class HTMLInput(InputFormatPlugin):