diff --git a/kalibrierschein/kalibrierschein.cls b/kalibrierschein/kalibrierschein.cls
index 6f69c5a9b69ce117064e4ff1bd32ee97c45803b1..50916aa69f171b0ab68b7aefc7067bde28da7de2 100644
--- a/kalibrierschein/kalibrierschein.cls
+++ b/kalibrierschein/kalibrierschein.cls
@@ -231,7 +231,7 @@
   \ks@tab\expandafter{\@tempa}%
   \ks@addTabLine{\ks@type}%
   \ks@add{\tabularnewline[#2]}%
-  \ks@addTabLine{\ks@serialNo}%
+  \ks@addTabLine{\noexpand\the\noexpand\ks@serialNo}%
   \ks@add{\end{tabularx}}%
   \begingroup
     \tabcolsep=1em %
@@ -282,9 +282,12 @@
   \{Name des Auftraggebers, Stra\ss e, Firmensitz\}}
 \newcommand*\applicant[1]{\xdef\ks@applicant{\trim@spaces{#1}}}
 
-\newcommand*\ks@serialNo{%
-  \{Nummer des untersuchten Ger\"ates, Normals, Pr\"aparats\}}
-\newcommand*\serialNo[1]{\xdef\ks@serialNo{\trim@spaces{#1}}}
+\RequirePackage{url}
+\DeclareUrlCommand\ks@@shielded{\urlstyle{same}}
+\newtoks\ks@serialNo
+\newcommand*\serialNo[1]{%
+  \ks@serialNo{\ks@@shielded{#1}}%
+}
 
 \newcommand*\ks@refNo{\{YYY-ZZZZZZZZ\}}
 \newcommand*\refNo[1]{\xdef\ks@refNo{\trim@spaces{#1}}}
@@ -438,12 +441,6 @@
   \fi
 }
 
-\RequirePackage{url}
-\DeclareUrlCommand\ks@@shielded{\urlstyle{same}}
-\newcommand*\ks@shielded[1]{%
-  \expandafter\ks@@shielded\expandafter{#1}%
-}
-
 \RequirePackage[
 % factor=1500
 % ,verbose=true
diff --git a/kalibrierschein/test-ks-KK-2015.tex b/kalibrierschein/test-ks-KK-2015.tex
index 4882e934c56cab10ba017d9f766cd36588f2b3a5..7789bb914124322a73c01af365ead872286eca8d 100644
--- a/kalibrierschein/test-ks-KK-2015.tex
+++ b/kalibrierschein/test-ks-KK-2015.tex
@@ -26,7 +26,7 @@ mbar&mbar&mbar&mbar&&\\\toprule\endhead
 \object{ Stabil Ion Gauge }
 \manufacturer{ Granville-Phillips }
 \type{ EXT-Y, Stabil Ion Controler 370B }
-\serialNo{ YEA06800, 1449 }
+\serialNo{ YEA06800, # & _ ^ 1449 }
 \applicant{  { BOC EDWARDS }  { Marshall Road }  { EASTBOURNE, EAST SUSSEX }  { BN22 9BA } }
 \refNo{ ? }
 \calibMark{ 75120 PTB 13 }