diff --git a/gnucash/report/report-system/html-document.scm b/gnucash/report/report-system/html-document.scm
index 906ab30b89..baf0c6aecb 100644
--- a/gnucash/report/report-system/html-document.scm
+++ b/gnucash/report/report-system/html-document.scm
@@ -141,6 +141,7 @@
             ;;./share/gnucash/scm/gnucash/report/taxinvoice.eguile.scm:<html>
             ;;./share/gnucash/scm/gnucash/report/balsheet-eg.eguile.scm:<html>
 
+            (push "<!DOCTYPE html>\n")
             (push "<html dir='auto'>\n")
             (push "<head>\n")
             (push "<meta http-equiv=\"content-type\" content=\"text/html; charset=utf-8\" />\n")
