diff --git a/include/crm/common/iso8601_internal.h b/include/crm/common/iso8601_internal.h
index 9a195941c1..d7ceee8e34 100644
--- a/include/crm/common/iso8601_internal.h
+++ b/include/crm/common/iso8601_internal.h
@@ -1,44 +1,47 @@
 /*
  * Copyright (C) 2015 Andrew Beekhof <andrew@beekhof.net>
  *
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This software is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * General Public License for more details.
  *
  * You should have received a copy of the GNU Lesser General Public
  * License along with this library; if not, write to the Free Software
  * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
  */
 
+#ifndef CRM_COMMON_ISO8601_INTERNAL
+#  define CRM_COMMON_ISO8601_INTERNAL
 #include <time.h>
 #include <sys/time.h>
 #include <ctype.h>
 #include <crm/common/iso8601.h>
 
 typedef struct crm_time_us crm_time_hr_t;
 crm_time_hr_t *crm_time_hr_convert(crm_time_hr_t *target, crm_time_t *dt);
 void crm_time_set_hr_dt(crm_time_t *target, crm_time_hr_t *hr_dt);
 crm_time_hr_t *crm_time_timeval_hr_convert(crm_time_hr_t *target,
                                            struct timeval *tv);
 crm_time_hr_t *crm_time_hr_new(const char *date_time);
 void crm_time_hr_free(crm_time_hr_t * hr_dt);
 char *crm_time_format_hr(const char *format, crm_time_hr_t * hr_dt);
 
 crm_time_t *parse_date(const char *date_str); /* in iso8601.c global but
                                                  not in header */
 
 struct crm_time_us {
     int years;
     int months;                 /* Only for durations */
     int days;
     int seconds;
     int offset;                 /* Seconds */
     bool duration;
     int useconds;
 };
+#endif