diff -ur kdebase-3.5.8/kdesu/configure.in.in kdebase-3.5.8-glibc28/kdesu/configure.in.in
--- kdebase-3.5.8/kdesu/configure.in.in	2006-10-05 18:24:50.000000000 +0200
+++ kdebase-3.5.8-glibc28/kdesu/configure.in.in	2008-02-09 08:20:31.000000000 +0100
@@ -1,6 +1,9 @@
 dnl Check for "struct ucred"
 AC_MSG_CHECKING("struct ucred")
-AC_EGREP_HEADER([struct ucred], [sys/socket.h], have_ucred=yes)
+AC_EGREP_CPP([struct ucred], [
+    #define _GNU_SOURCE
+    #include <sys/socket.h>
+], have_ucred=yes)
 if test "$have_ucred" = "yes"; then
     AC_DEFINE(HAVE_STRUCT_UCRED, 1, [Define if you have the struct ucred])
     AC_MSG_RESULT(yes)