--- a/configure.ac
+++ b/configure.ac
@@ -39,7 +39,7 @@ AC_ARG_WITH(pam,
     fi,
 )
 
-if test "use_pam" != "no"; then
+if test "$use_pam" != "no"; then
   have_pam=yes
   AC_CHECK_HEADER(security/pam_appl.h, [], [have_pam=no])
   if test "$have_pam" = "yes"; then
