diff --git a/doc/_sphinx/conf.py b/doc/_sphinx/conf.py
index 7551fc35a..12d4dee8a 100644
--- a/doc/_sphinx/conf.py
+++ b/doc/_sphinx/conf.py
@@ -93,6 +93,7 @@ pygments_style = 'monokai'
 # so a file named "default.css" will overwrite the builtin "default.css".
 html_static_path = ['images', 'scripts', 'theme']
 html_js_files = ['versions.js', 'menu-expand.js']
+html_css_files = ["copy-button.css"]
 
 
 # -- Custom setup ------------------------------------------------------------