diff --git a/doc/frama-c-book.cls b/doc/frama-c-book.cls
index b605d8df6105c42af7edc0d65a6c116737f9186d..f785b0f1d5d85f06c391567a867b6e1de4048110 100644
--- a/doc/frama-c-book.cls
+++ b/doc/frama-c-book.cls
@@ -312,6 +312,7 @@
 \fancyhead[L]{\vspace{1.25em}\raggedleft\rightmark\vspace{-1.25em}}
 \fancyfoot[C]{\thepage}
 \renewcommand{\headrulewidth}{0pt}
+\setlength{\headheight}{24pt}
 
 % --------------------------------------------------------------------------
 % Chapters