diff --git a/answer.h b/answer.h
index acb3665af..43ae584b9 100644
--- a/answer.h
+++ b/answer.h
@@ -7,8 +7,8 @@
  *
  */
 
-#ifndef _ANSWER_H_
-#define _ANSWER_H_
+#ifndef ANSWER_H
+#define ANSWER_H
 
 #include <sys/types.h>
 
@@ -44,4 +44,4 @@ int answer_add_rrset(answer_type *answer, rr_section_type section,
 		     domain_type *domain, rrset_type *rrset);
 
 
-#endif /* _ANSWER_H_ */
+#endif /* ANSWER_H */
diff --git a/axfr.h b/axfr.h
index 105cd5362..7f80d1838 100644
--- a/axfr.h
+++ b/axfr.h
@@ -7,8 +7,8 @@
  *
  */
 
-#ifndef _AXFR_H_
-#define _AXFR_H_
+#ifndef AXFR_H
+#define AXFR_H
 
 #include "nsd.h"
 #include "query.h"
@@ -22,4 +22,4 @@
 query_state_type answer_axfr_ixfr(struct nsd *nsd, struct query *q);
 query_state_type query_axfr(struct nsd *nsd, struct query *query, int wstats);
 
-#endif /* _AXFR_H_ */
+#endif /* AXFR_H */
diff --git a/bitset.h b/bitset.h
index 85ed3bfb1..ddd974765 100644
--- a/bitset.h
+++ b/bitset.h
@@ -6,8 +6,8 @@
  * See LICENSE for the license.
  *
  */
-#ifndef _BITSET_H_
-#define _BITSET_H_
+#ifndef BITSET_H
+#define BITSET_H
 
 #include <assert.h>
 #include <limits.h>
@@ -37,4 +37,4 @@ void nsd_bitset_or(
 	struct nsd_bitset *srcset1,
 	struct nsd_bitset *srcset2);
 
-#endif /* _BITSET_H_ */
+#endif /* BITSET_H */
diff --git a/buffer.h b/buffer.h
index 9e17bc958..9cf532147 100644
--- a/buffer.h
+++ b/buffer.h
@@ -10,8 +10,8 @@
  * the java.nio.Buffer interface.
  */
 
-#ifndef _BUFFER_H_
-#define _BUFFER_H_
+#ifndef BUFFER_H
+#define BUFFER_H
 
 #include <assert.h>
 #include <stdarg.h>
@@ -411,4 +411,4 @@ buffer_read_u64(buffer_type *buffer)
 int buffer_printf(buffer_type *buffer, const char *format, ...)
 	ATTR_FORMAT(printf, 2, 3);
 
-#endif /* _BUFFER_H_ */
+#endif /* BUFFER_H */
diff --git a/compat/cpuset.h b/compat/cpuset.h
index 5a30761e0..a53fbf38a 100644
--- a/compat/cpuset.h
+++ b/compat/cpuset.h
@@ -6,8 +6,8 @@
  * See LICENSE for the license.
  *
  */
-#ifndef _CPUSET_H_
-#define _CPUSET_H_
+#ifndef CPUSET_H
+#define CPUSET_H
 
 #ifdef HAVE_SCHED_H
 # include <sched.h>
@@ -76,4 +76,4 @@ size_t cpuset_size(const cpuset_t *set);
 
 void cpuset_or(cpuset_t *destset, const cpuset_t *srcset);
 
-#endif /* _CPUSET_H_ */
+#endif /* CPUSET_H */
diff --git a/compat/fake-rfc2553.h b/compat/fake-rfc2553.h
index efae6dc1e..0a0af693b 100644
--- a/compat/fake-rfc2553.h
+++ b/compat/fake-rfc2553.h
@@ -36,8 +36,8 @@
  * that ai_family is AF_INET. Don't use it for another purpose.
  */
 
-#ifndef _FAKE_RFC2553_H
-#define _FAKE_RFC2553_H
+#ifndef FAKE_RFC2553_H
+#define FAKE_RFC2553_H
 
 #include <config.h>
 #include <sys/types.h>
@@ -177,5 +177,5 @@ int getnameinfo(const struct sockaddr *, size_t, char *, size_t,
     char *, size_t, int);
 #endif /* !HAVE_GETNAMEINFO */
 
-#endif /* !_FAKE_RFC2553_H */
+#endif /* !FAKE_RFC2553_H */
 
diff --git a/dname.h b/dname.h
index 188ade18d..0d5dc4ac8 100644
--- a/dname.h
+++ b/dname.h
@@ -7,8 +7,8 @@
  *
  */
 
-#ifndef _DNAME_H_
-#define _DNAME_H_
+#ifndef DNAME_H
+#define DNAME_H
 
 #include <assert.h>
 #include <stdio.h>
@@ -381,4 +381,4 @@ char* wirelabel2str(const uint8_t* label);
 /** check if two uncompressed dnames of the same total length are equal */
 int dname_equal_nocase(uint8_t* a, uint8_t* b, uint16_t len);
 
-#endif /* _DNAME_H_ */
+#endif /* DNAME_H */
diff --git a/dns.h b/dns.h
index 344e8cc48..924db3de0 100644
--- a/dns.h
+++ b/dns.h
@@ -7,8 +7,8 @@
  *
  */
 
-#ifndef _DNS_H_
-#define _DNS_H_
+#ifndef DNS_H
+#define DNS_H
 
 enum rr_section {
 	QUESTION_SECTION,
@@ -305,4 +305,4 @@ operator++(rr_section_type &lhs)
 }
 #endif /* __cplusplus */
 
-#endif /* _DNS_H_ */
+#endif /* DNS_H */
diff --git a/doc/ChangeLog b/doc/ChangeLog
index 25da7515a..4d41558ca 100644
--- a/doc/ChangeLog
+++ b/doc/ChangeLog
@@ -1,3 +1,6 @@
+23 February 2022: Wouter
+	- Fix #270: reserved identifier violation.
+
 20 February 2022: Wouter
 	- Merge #269 from Fale: Add systemd service unit.
 
diff --git a/doc/RELNOTES b/doc/RELNOTES
index fc576ec66..74b498ea8 100644
--- a/doc/RELNOTES
+++ b/doc/RELNOTES
@@ -15,6 +15,7 @@ BUG FIXES:
 	- Merge #265: Fix C99 compatibility issue.
 	- Fix #266: Fix build with --without-ssl.
 	- Fix for #267: neater variable definitions.
+	- Fix #270: reserved identifier violation.
 
 4.6.1
 ================
diff --git a/edns.h b/edns.h
index 942312c03..45d7c6361 100644
--- a/edns.h
+++ b/edns.h
@@ -7,8 +7,8 @@
  *
  */
 
-#ifndef _EDNS_H_
-#define _EDNS_H_
+#ifndef EDNS_H
+#define EDNS_H
 
 #include "buffer.h"
 struct nsd;
@@ -103,4 +103,4 @@ void edns_init_nsid(edns_data_type *data, uint16_t nsid_len);
 void cookie_verify(struct query *q, struct nsd* nsd, uint32_t *now_p);
 void cookie_create(struct query *q, struct nsd* nsd, uint32_t *now_p);
 
-#endif /* _EDNS_H_ */
+#endif /* EDNS_H */
diff --git a/ixfr.h b/ixfr.h
index 0f201038b..0920dc132 100644
--- a/ixfr.h
+++ b/ixfr.h
@@ -7,8 +7,8 @@
  *
  */
 
-#ifndef _IXFR_H_
-#define _IXFR_H_
+#ifndef IXFR_H
+#define IXFR_H
 struct nsd;
 #include "query.h"
 #include "rbtree.h"
@@ -265,4 +265,4 @@ int ixfr_unlink_it(const char* zname, const char* zfile, int file_num,
 void ixfr_delete_superfluous_files(struct zone* zone, const char* zfile,
 	int dest_num_files);
 
-#endif /* _IXFR_H_ */
+#endif /* IXFR_H */
diff --git a/ixfrcreate.h b/ixfrcreate.h
index c09e0b1b7..0446d2cb0 100644
--- a/ixfrcreate.h
+++ b/ixfrcreate.h
@@ -7,8 +7,8 @@
  *
  */
 
-#ifndef _IXFRCREATE_H_
-#define _IXFRCREATE_H_
+#ifndef IXFRCREATE_H
+#define IXFRCREATE_H
 #include "dns.h"
 struct zone;
 struct nsd;
@@ -83,4 +83,4 @@ struct spool_dname_iterator {
 	char* file_name;
 };
 
-#endif /* _IXFRCREATE_H_ */
+#endif /* IXFRCREATE_H */
diff --git a/namedb.h b/namedb.h
index e20d1cac6..3143e867d 100644
--- a/namedb.h
+++ b/namedb.h
@@ -7,8 +7,8 @@
  *
  */
 
-#ifndef _NAMEDB_H_
-#define	_NAMEDB_H_
+#ifndef NAMEDB_H
+#define	NAMEDB_H
 
 #include <stdio.h>
 
@@ -466,4 +466,4 @@ void zone_rr_iter_init(zone_rr_iter_type *iter, zone_type *zone);
 
 rr_type *zone_rr_iter_next(zone_rr_iter_type *iter);
 
-#endif /* _NAMEDB_H_ */
+#endif /* NAMEDB_H */
diff --git a/netio.h b/netio.h
index a0e805e9e..485435248 100644
--- a/netio.h
+++ b/netio.h
@@ -38,8 +38,8 @@
  * blocked in pselect(2).
  */
 
-#ifndef _NETIO_H_
-#define _NETIO_H_
+#ifndef NETIO_H
+#define NETIO_H
 
 #ifdef	HAVE_SYS_SELECT_H
 #include <sys/select.h>
@@ -187,4 +187,4 @@ operator |= (netio_event_types_type &lhs, netio_event_types_type rhs) {
 }
 #endif /* __cplusplus */
 
-#endif /* _NETIO_H_ */
+#endif /* NETIO_H */
diff --git a/nsd.h b/nsd.h
index f7cd53817..8fea49d6d 100644
--- a/nsd.h
+++ b/nsd.h
@@ -7,8 +7,8 @@
  *
  */
 
-#ifndef	_NSD_H_
-#define	_NSD_H_
+#ifndef	NSD_H
+#define	NSD_H
 
 #include <signal.h>
 #include <net/if.h>
@@ -407,4 +407,4 @@ void perform_openssl_init(void);
 #endif
 ssize_t block_read(struct nsd* nsd, int s, void* p, ssize_t sz, int timeout);
 
-#endif	/* _NSD_H_ */
+#endif	/* NSD_H */
diff --git a/packet.h b/packet.h
index ed08dfae1..9b4a524cd 100644
--- a/packet.h
+++ b/packet.h
@@ -7,8 +7,8 @@
  *
  */
 
-#ifndef _PACKET_H_
-#define _PACKET_H_
+#ifndef PACKET_H
+#define PACKET_H
 
 #include <sys/types.h>
 
@@ -202,4 +202,4 @@ int packet_read_query_section(buffer_type *packet,
  * returns false on no-serial found or parse failure. */
 int packet_find_notify_serial(buffer_type *packet, uint32_t* serial);
 
-#endif /* _PACKET_H_ */
+#endif /* PACKET_H */
diff --git a/popen3.h b/popen3.h
index ed95b500f..82d84d878 100644
--- a/popen3.h
+++ b/popen3.h
@@ -6,8 +6,8 @@
  * See LICENSE for the license.
  *
  */
-#ifndef _POPEN3_H_
-#define _POPEN3_H_
+#ifndef POPEN3_H
+#define POPEN3_H
 
 #include <stdio.h>
 #include <sys/types.h>
@@ -24,4 +24,4 @@ pid_t popen3(char *const *command,
              int *fdoutptr,
              int *fderrptr);
 
-#endif /* _POPEN3_H_ */
+#endif /* POPEN3_H */
diff --git a/query.h b/query.h
index 2f47c9371..e68229019 100644
--- a/query.h
+++ b/query.h
@@ -7,8 +7,8 @@
  *
  */
 
-#ifndef _QUERY_H_
-#define _QUERY_H_
+#ifndef QUERY_H
+#define QUERY_H
 
 #include <assert.h>
 #include <string.h>
@@ -230,4 +230,4 @@ query_overflow(query_type *q)
 {
 	return buffer_position(q->packet) > (q->maxlen - q->reserved_space);
 }
-#endif /* _QUERY_H_ */
+#endif /* QUERY_H */
diff --git a/rbtree.h b/rbtree.h
index eb9b39412..0dea2097c 100644
--- a/rbtree.h
+++ b/rbtree.h
@@ -7,8 +7,8 @@
  *
  */
 
-#ifndef _RBTREE_H_
-#define	_RBTREE_H_
+#ifndef RBTREE_H
+#define	RBTREE_H
 
 #include "region-allocator.h"
 
@@ -73,4 +73,4 @@ rbnode_type *rbtree_previous(rbnode_type *rbtree);
 		(rbnode_type*)node != RBTREE_NULL; \
 		node = (type)rbtree_next((rbnode_type*)node))
 
-#endif /* _RBTREE_H_ */
+#endif /* RBTREE_H */
diff --git a/rdata.h b/rdata.h
index 457d940ec..deaa6eff7 100644
--- a/rdata.h
+++ b/rdata.h
@@ -7,8 +7,8 @@
  *
  */
 
-#ifndef _RDATA_H_
-#define _RDATA_H_
+#ifndef RDATA_H
+#define RDATA_H
 
 #include "dns.h"
 #include "namedb.h"
@@ -58,4 +58,4 @@ int rdata_atoms_to_unknown_string(buffer_type *out,
 int print_rdata(buffer_type *output, rrtype_descriptor_type *descriptor,
             rr_type *record);
 
-#endif /* _DNS_H_ */
+#endif /* RDATA_H */
diff --git a/region-allocator.h b/region-allocator.h
index b305f1c9b..99af23350 100644
--- a/region-allocator.h
+++ b/region-allocator.h
@@ -7,8 +7,8 @@
  *
  */
 
-#ifndef _REGION_ALLOCATOR_H_
-#define _REGION_ALLOCATOR_H_
+#ifndef REGION_ALLOCATOR_H
+#define REGION_ALLOCATOR_H
 
 #include <stdio.h>
 
@@ -150,4 +150,4 @@ size_t region_get_mem_unused(region_type* region);
 /* Debug print REGION statistics to LOG. */
 void region_log_stats(region_type *region);
 
-#endif /* _REGION_ALLOCATOR_H_ */
+#endif /* REGION_ALLOCATOR_H */
diff --git a/tsig-openssl.h b/tsig-openssl.h
index c3c9b2359..13824a5e6 100644
--- a/tsig-openssl.h
+++ b/tsig-openssl.h
@@ -7,8 +7,8 @@
  *
  */
 
-#ifndef _TSIG_OPENSSL_H_
-#define _TSIG_OPENSSL_H_
+#ifndef TSIG_OPENSSL_H
+#define TSIG_OPENSSL_H
 
 #if defined(HAVE_SSL)
 
@@ -26,4 +26,4 @@ void tsig_openssl_finalize(void);
 
 #endif /* defined(HAVE_SSL) */
 
-#endif /* _TSIG_H_ */
+#endif /* TSIG_OPENSSL_H */
diff --git a/tsig.h b/tsig.h
index 1c2c12117..4f74dd276 100644
--- a/tsig.h
+++ b/tsig.h
@@ -7,8 +7,8 @@
  *
  */
 
-#ifndef _TSIG_H_
-#define _TSIG_H_
+#ifndef TSIG_H
+#define TSIG_H
 
 #include <sys/types.h>
 #include <sys/socket.h>
@@ -289,4 +289,4 @@ int tsig_strlowercmp(const char* str1, const char* str2);
  */
 void tsig_finalize(void);
 
-#endif /* _TSIG_H_ */
+#endif /* TSIG_H */
diff --git a/util.h b/util.h
index 332d5d30d..97b7ba0cf 100644
--- a/util.h
+++ b/util.h
@@ -7,8 +7,8 @@
  *
  */
 
-#ifndef _UTIL_H_
-#define _UTIL_H_
+#ifndef UTIL_H
+#define UTIL_H
 
 #include <sys/time.h>
 #include <stdarg.h>
@@ -451,4 +451,4 @@ void activate_cookie_secret(struct nsd* nsd);
 /* Drop a cookie secret. Drops the staging secret. An active secret will not
  * be dropped. */
 void drop_cookie_secret(struct nsd* nsd);
-#endif /* _UTIL_H_ */
+#endif /* UTIL_H */
diff --git a/verify.h b/verify.h
index 7333b9188..1d50f622f 100644
--- a/verify.h
+++ b/verify.h
@@ -5,8 +5,8 @@
  *
  * See LICENSE for the license.
  */
-#ifndef _VERIFY_H_
-#define _VERIFY_H_
+#ifndef VERIFY_H
+#define VERIFY_H
 
 #ifndef USE_MINI_EVENT
 #  ifdef HAVE_EVENT_H
@@ -77,4 +77,4 @@ void verify_handle_exit(int fd, short event, void *arg);
 
 void verify_handle_command(int fd, short event, void *arg);
 
-#endif /* _VERIFY_H_ */
+#endif /* VERIFY_H */
diff --git a/zonec.h b/zonec.h
index e1b1fdd54..d4db32e0f 100644
--- a/zonec.h
+++ b/zonec.h
@@ -7,8 +7,8 @@
  *
  */
 
-#ifndef _ZONEC_H_
-#define _ZONEC_H_
+#ifndef ZONEC_H
+#define ZONEC_H
 
 #include "namedb.h"
 
@@ -150,4 +150,4 @@ void check_sshfp(void);
 void apex_rrset_checks(struct namedb* db, rrset_type* rrset,
 	domain_type* domain);
 
-#endif /* _ZONEC_H_ */
+#endif /* ZONEC_H */