--- silc-toolkit-1.1.10.orig/configure
+++ silc-toolkit-1.1.10/configure
@@ -3049,7 +3049,7 @@
 # Put here any platform specific stuff
 #
 case "$target" in
-  *-*-linux*)
+  *-*-linux*|*-k*bsd*-gnu)
     check_threads=true
     CFLAGS=`echo $CFLAGS -D_GNU_SOURCE`
     ;;