diff --git a/.gitlab/pipeline/build.yml b/.gitlab/pipeline/build.yml
index 328b37af1d4d..924d648e3f98 100644
--- a/.gitlab/pipeline/build.yml
+++ b/.gitlab/pipeline/build.yml
@@ -111,6 +111,9 @@ build-rustdoc:
             sed -i "s|</head>|$script_content</head>|" "$file"
         }
         export -f process_file
+        # xargs runs process_file in seperate shells without access to outer variables.
+        # to make script_content available inside process_file, export it as an env var here.
+        export script_content
 
         # Modify .html files in parallel using xargs, otherwise it can take a long time.
         find "$path" -name '*.html' | xargs -I {} -P "$(nproc)" bash -c 'process_file "$@"' _ {}