diff --git a/common/rtemsstyle.sty b/common/rtemsstyle.sty
index 6761b96..033b494 100644
--- a/common/rtemsstyle.sty
+++ b/common/rtemsstyle.sty
@@ -10,6 +10,10 @@
 
 \renewenvironment{tabulary}{\underscoresplit\oldtabulary}{\endoldtabulary\endunderscoresplit}
 
+\let\oldprintindex\printindex
+
+\renewenvironment{printindex}{\underscoresplit\oldprintindex}
+
 
 \renewcommand{\maketitle}{%
   \begin{titlepage}%