diff --git a/fhem/CHANGED b/fhem/CHANGED
index 78afe7240..dab7be9aa 100644
--- a/fhem/CHANGED
+++ b/fhem/CHANGED
@@ -4,6 +4,7 @@
   - feature: PID rewrite (and moved from contrib into the FHEM directory).
   - feature: FHEM2FHEM module
   - bugfix:  CUL get should not digest foreign events (fhtsoftbuffer)
+  - bugfix:  S300TH sanity check won't allow negative temperatures.
 
 - 2010-08-15 (5.0)
   - **NOTE*: The default installation path is changed to satisfy lintian
diff --git a/fhem/FHEM/14_CUL_WS.pm b/fhem/FHEM/14_CUL_WS.pm
index 20cfae858..04a611eef 100755
--- a/fhem/FHEM/14_CUL_WS.pm
+++ b/fhem/FHEM/14_CUL_WS.pm
@@ -1,4 +1,4 @@
-# $Id: 14_CUL_WS.pm,v 1.28 2010-08-19 18:42:06 wherzig Exp $
+# $Id: 14_CUL_WS.pm,v 1.29 2010-10-24 17:17:24 rudolfkoenig Exp $
 #
 ##############################################
 package main;
@@ -231,7 +231,7 @@ CUL_WS_Parse($$)
 
     if(@a == 9 && int(@a) > 8) {                 #  S300TH
       # Sanity check
-      if (!($msg =~ /^K\d\d\d\d\d\d\d\d$/ )) {
+      if (!($msg =~ /^K[0-9A-F]\d\d\d\d\d\d\d$/ )) {
         Log GetLogLevel($name,1), "Error: S300TH CUL_WS Cannot decode $msg (sanitycheck). Malformed";
         return "";
       }