diff --git a/header.md b/header.md
index 9fdfd01..56129fa 100644
--- a/header.md
+++ b/header.md
@@ -2,6 +2,7 @@
 documentclass: extarticle
 fontsize: 14pt
 geometry: margin=2cm
+papersize: a4
 header-includes: | 
   \usepackage{pdfpages}
   \usepackage{trfsigns}