diff --git a/buildtools/call-sphinx-build.py b/buildtools/call-sphinx-build.py
index da19e950c92..623e7363ee7 100755
--- a/buildtools/call-sphinx-build.py
+++ b/buildtools/call-sphinx-build.py
@@ -3,6 +3,8 @@
 # Copyright(c) 2019 Intel Corporation
 #
 
+import filecmp
+import shutil
 import sys
 import os
 from os.path import join
@@ -30,4 +32,12 @@
 with open(join(dst, '.html.d'), 'w') as d:
     d.write('html: ' + ' '.join(srcfiles) + '\n')
 
+# copy custom CSS file
+css = 'custom.css'
+src_css = join(src, css)
+dst_css = join(dst, 'html', '_static', 'css', css)
+if not os.path.exists(dst_css) or not filecmp.cmp(src_css, dst_css):
+    os.makedirs(os.path.dirname(dst_css), exist_ok=True)
+    shutil.copyfile(src_css, dst_css)
+
 sys.exit(process.returncode)
diff --git a/doc/guides/meson.build b/doc/guides/meson.build
index 51f81da2e37..f8bbfba9f5b 100644
--- a/doc/guides/meson.build
+++ b/doc/guides/meson.build
@@ -24,7 +24,5 @@ html_guides = custom_target('html_guides',
         install: get_option('enable_docs'),
         install_dir: htmldir)
 
-install_data(files('custom.css'), install_dir: join_paths(htmldir,'_static', 'css'))
-
 doc_targets += html_guides
 doc_target_names += 'HTML_Guides'