diff --git a/cf/check-var.m4 b/cf/check-var.m4
index 59e15d767..67758a583 100644
--- a/cf/check-var.m4
+++ b/cf/check-var.m4
@@ -4,10 +4,17 @@ dnl rk_CHECK_VAR(variable, includes)
 AC_DEFUN([rk_CHECK_VAR], [
 AC_MSG_CHECKING(for $1)
 AC_CACHE_VAL(ac_cv_var_$1, [
+m4_ifval([$2],[
+	AC_TRY_LINK([$2
+	void * foo() { return &$1; }],
+	    [foo()],
+	    ac_cv_var_$1=yes, ac_cv_var_$1=no)])
+if test "$ac_cv_var_$1" != yes ; then
 AC_TRY_LINK([extern int $1;
 int foo() { return $1; }],
 	    [foo()],
 	    ac_cv_var_$1=yes, ac_cv_var_$1=no)
+fi
 ])
 ac_foo=`eval echo \\$ac_cv_var_$1`
 AC_MSG_RESULT($ac_foo)
@@ -19,4 +26,4 @@ fi
 ])
 
 AC_WARNING_ENABLE([obsolete])
-AU_DEFUN([AC_CHECK_VAR], [rk_CHECK_VAR([$2], [$1])], [foo])
\ No newline at end of file
+AU_DEFUN([AC_CHECK_VAR], [rk_CHECK_VAR([$2], [$1])], [foo])