diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index ef81e7db0abd2bd3e208173803739eee62897c8d..3163e056a559913bf55d32c6485ca35e52c3f95f 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -51,7 +51,7 @@ pages:
                -o ${TARGET} ../slides/${MDFILE} \
                -V revealjs-url=https://unpkg.com/reveal.js/ \
                -V theme=${REVEAL_THEME} \
-               --include-in-header=../slides/dumux_course_header.html
+               --css=../slides/dumux_course.css
       done
     cd ..
   - mkdir public && mv build/* public && cp -r slides/img public
diff --git a/slides/dumux_course_header.html b/slides/dumux_course.css
similarity index 97%
rename from slides/dumux_course_header.html
rename to slides/dumux_course.css
index 57d4146013914b426dc582bd9931650e817b3404..8a8f0f73f557e78440acca86ca1b7b11f4fb6848 100644
--- a/slides/dumux_course_header.html
+++ b/slides/dumux_course.css
@@ -1,4 +1,3 @@
-<style>
 @import url("https://fonts.googleapis.com/css?family=Nanum+Gothic");
 
 :root {
@@ -46,4 +45,3 @@
     font-size: 1.75em;
     font-family: var(--font-family), sans-serif;
 }
-</style>