diff --git a/ptbposter/ptbposter.cls b/ptbposter/ptbposter.cls
index ad775cfb9051ffac6f8b0618d04412d91816c72e..c29b1fa5ffbab4b67e332e4fdf3ae4959eeb9d53 100644
--- a/ptbposter/ptbposter.cls
+++ b/ptbposter/ptbposter.cls
@@ -330,6 +330,8 @@
   \PTBlandscapetrue
 \fi
 
+\RequirePackage{relsize}\renewcommand\RSpercentTolerance{0}
+
 \newcommand*\scaleFontSizes[1]{%
   \global\PTB@default@fsize=#1\PTB@default@fontsize@base
 }
@@ -489,6 +491,10 @@
 ]{subparagraph}
 }
 
+\newcommand*\suppressBibHeader{% no head line for bibliography (\refname)  
+  \let\bib@heading=\relax 
+}
+
 \setcounter{secnumdepth}{-2}
 \renewcommand*\maketitle[1][1]{}
 \renewcommand*\tableofcontents{}