diff --git a/CMakeLists.txt b/CMakeLists.txt
index da3d09d2..cd6cc3f2 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -361,6 +361,20 @@ check_function_exists(getopt HAVE_GETOPT)
 if(HAVE_GETOPT)
         add_definitions(-DHAVE_GETOPT)
 endif()
+
+check_function_exists(ibuf_add_buf HAVE_IBUF_ADD_BUF)
+if(HAVE_IBUF_ADD_BUF)
+        add_definitions(-DHAVE_IBUF_ADD_BUF)
+endif()
+check_function_exists(ibuf_add_zero HAVE_IBUF_ADD_ZERO)
+if(HAVE_IBUF_ADD_ZERO)
+        add_definitions(-DHAVE_IBUF_ADD_ZERO)
+endif()
+check_function_exists(ibuf_data HAVE_IBUF_DATA)
+if(HAVE_IBUF_DATA)
+        add_definitions(-DHAVE_IBUF_DATA)
+endif()
+
 if(HAVE_VROUTE OR HAVE_VROUTE_NETLINK)
 	add_definitions(-DHAVE_VROUTE)
 endif()
diff --git a/compat/CMakeLists.txt b/compat/CMakeLists.txt
index 69027c18..b714c139 100644
--- a/compat/CMakeLists.txt
+++ b/compat/CMakeLists.txt
@@ -73,6 +73,9 @@ endif()
 if(NOT HAVE_VIS)
 	list(APPEND SRCS ${IKED_COMPAT}/vis.c)
 endif()
+if(NOT HAVE_IBUF_ADD_BUF OR NOT HAVE_IBUF_ADD_ZERO OR NOT HAVE_IBUF_DATA)
+	list(APPEND SRCS ${IKED_COMPAT}/ibuf-compat.c)
+endif()
 
 set(CFLAGS)
 list(APPEND CFLAGS
diff --git a/compat/ibuf-compat.c b/compat/ibuf-compat.c
new file mode 100644
index 00000000..72bf329d
--- /dev/null
+++ b/compat/ibuf-compat.c
@@ -0,0 +1,76 @@
+/*      $OpenBSD: imsg-buffer.c,v 1.16 2023/06/19 17:19:50 claudio Exp $        */
+
+/*
+ * Copyright (c) 2003, 2004 Henning Brauer <henning@openbsd.org>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+/* ibuf API functions added to OpenBSD's imsg-buffer.c in June 2023. */
+
+#ifdef HAVE_IMSG_H
+
+#if !defined(HAVE_IBUF_ADD_BUF) || !defined(HAVE_IBUF_ADD_ZERO)
+#include <sys/queue.h>
+
+#include <string.h>
+#include <imsg.h>
+#endif /* !defined(HAVE_IBUF_ADD_BUF) || !defined(HAVE_IBUF_ADD_ZERO) */
+
+#if !defined(HAVE_IBUF_ADD_BUF)
+void *ibuf_reserve(struct ibuf *, size_t);
+
+int
+ibuf_add(struct ibuf *buf, const void *data, size_t len)
+{
+	void *b;
+
+	if ((b = ibuf_reserve(buf, len)) == NULL)
+		return (-1);
+
+	memcpy(b, data, len);
+	return (0);
+}
+
+int
+ibuf_add_buf(struct ibuf *buf, const struct ibuf *from)
+{
+	return ibuf_add(buf, from->buf, from->wpos);
+}
+#endif /* !defined(HAVE_IBUF_ADD_BUF) */
+
+#if !defined(HAVE_IBUF_ADD_ZERO)
+void *ibuf_reserve(struct ibuf *, size_t);
+
+int
+ibuf_add_zero(struct ibuf *buf, size_t len)
+{
+	void *b;
+
+	if ((b = ibuf_reserve(buf, len)) == NULL)
+		return (-1);
+	return (0);
+}
+#endif /* !defined(HAVE_IBUF_ADD_ZERO) */
+
+#if !defined(HAVE_IBUF_DATA)
+void *ibuf_seek(struct ibuf *, size_t, size_t);
+
+void *
+ibuf_data(struct ibuf *buf)
+{
+	return (ibuf_seek(buf, 0, 0));
+}
+#endif /* !defined(HAVE_IBUF_DATA) */
+
+#endif /* HAVE_IMSG_H */