The barker preamble bit is set when a station associates which does not support
short preambles. When it is 0, short preambles are allowed.

Index: epan/dissectors/packet-ieee80211.c
===================================================================
--- epan/dissectors/packet-ieee80211.c	(revision 18775)
+++ epan/dissectors/packet-ieee80211.c	(working copy)
 <at>  <at>  -1834,7 +1834,7  <at>  <at> 
         g_snprintf (print_buff, SHORT_STR, "%sNon-ERP STAs, %suse protection, %s preambles",
                   erp_info & 0x01 ? "" : "no ",
                   erp_info & 0x02 ? "" : "do not ",
-                  erp_info & 0x04 ? "short or long": "long");
+                  erp_info & 0x04 ? "long" : "short or long");
         print_buff[SHORT_STR-1] = '\0';
         g_snprintf (out_buff, SHORT_STR,
                   "ERP info: 0x%x (%s)",erp_info,print_buff);