diff --git a/acinclude.m4 b/acinclude.m4
index 154dc6e9f..3f6a2e8b4 100644
--- a/acinclude.m4
+++ b/acinclude.m4
@@ -390,9 +390,9 @@ AC_DEFUN([CURL_CHECK_FUNC_GETNAMEINFO], [
         ;;
       esac
       #
-      AC_DEFINE_UNQUOTED(GETNAMEINFO_QUAL_ARG1, $gni_qual_arg1,
+      AC_DEFINE_UNQUOTED(GETNAMEINFO_QUAL_ARG1, "$gni_qual_arg1",
         [Define to the type qualifier of arg 1 for getnameinfo.])
-      AC_DEFINE_UNQUOTED(GETNAMEINFO_TYPE_ARG1, $gni_type_arg1,
+      AC_DEFINE_UNQUOTED(GETNAMEINFO_TYPE_ARG1, "$gni_type_arg1",
         [Define to the type of arg 1 for getnameinfo.])
       #
       AC_DEFINE_UNQUOTED(HAVE_GETNAMEINFO, 1,