diff --git a/include/os/freebsd/spl/sys/Makefile.am b/include/os/freebsd/spl/sys/Makefile.am
index 7d82e2d6d4..ca45b42b6b 100644
--- a/include/os/freebsd/spl/sys/Makefile.am
+++ b/include/os/freebsd/spl/sys/Makefile.am
@@ -15,6 +15,7 @@ KERNEL_H = \
 	disp.h \
 	dkio.h \
 	extdirent.h \
+	fcntl.h \
 	file.h \
 	freebsd_rwlock.h \
 	inttypes.h \
diff --git a/include/os/freebsd/spl/sys/ccompile.h b/include/os/freebsd/spl/sys/ccompile.h
index a02e8f0985..7109d42ffb 100644
--- a/include/os/freebsd/spl/sys/ccompile.h
+++ b/include/os/freebsd/spl/sys/ccompile.h
@@ -166,10 +166,6 @@ extern "C" {
 #define	ECHRNG ENXIO
 #define	ETIME ETIMEDOUT
 
-#define	O_LARGEFILE 0
-#define	O_RSYNC 0
-#define	O_DSYNC 0
-
 #ifndef LOCORE
 #ifndef HAVE_RPC_TYPES
 typedef int bool_t;
diff --git a/include/os/freebsd/spl/sys/fcntl.h b/include/os/freebsd/spl/sys/fcntl.h
new file mode 100644
index 0000000000..4301d6e151
--- /dev/null
+++ b/include/os/freebsd/spl/sys/fcntl.h
@@ -0,0 +1,38 @@
+/*
+ * Copyright (c) 2021 iXsystems, Inc.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#ifndef _SPL_SYS_FCNTL_H_
+#define	_SPL_SYS_FCNTL_H_
+
+#include_next <sys/fcntl.h>
+
+#define	O_LARGEFILE	0
+#define	O_RSYNC		0
+
+#ifndef O_DSYNC
+#define	O_DSYNC		0
+#endif
+
+#endif	/* _SPL_SYS_FCNTL_H_ */
diff --git a/include/os/freebsd/spl/sys/vnode.h b/include/os/freebsd/spl/sys/vnode.h
index 6a61461327..fa7bbd88c6 100644
--- a/include/os/freebsd/spl/sys/vnode.h
+++ b/include/os/freebsd/spl/sys/vnode.h
@@ -127,7 +127,9 @@ vn_is_readonly(vnode_t *vp)
 #define	FCREAT		O_CREAT
 #define	FTRUNC		O_TRUNC
 #define	FEXCL		O_EXCL
+#ifndef FDSYNC
 #define	FDSYNC		FFSYNC
+#endif
 #define	FRSYNC		FFSYNC
 #define	FSYNC		FFSYNC
 #define	FOFFMAX		0x00
diff --git a/lib/libspl/include/os/freebsd/Makefile.am b/lib/libspl/include/os/freebsd/Makefile.am
index 081839c48c..f06325ee3e 100644
--- a/lib/libspl/include/os/freebsd/Makefile.am
+++ b/lib/libspl/include/os/freebsd/Makefile.am
@@ -1 +1,5 @@
 SUBDIRS = sys
+
+libspldir = $(includedir)/libspl
+libspl_HEADERS = \
+	fcntl.h
diff --git a/lib/libspl/include/os/freebsd/fcntl.h b/lib/libspl/include/os/freebsd/fcntl.h
new file mode 100644
index 0000000000..26d571ad89
--- /dev/null
+++ b/lib/libspl/include/os/freebsd/fcntl.h
@@ -0,0 +1,33 @@
+/*
+ * Copyright (c) 2021 iXsystems, Inc.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#ifndef _LIBSPL_FCNTL_H_
+#define	_LIBSPL_FCNTL_H_
+
+#include_next <fcntl.h>
+
+#include <sys/fcntl.h>
+
+#endif	/* _LIBSPL_FCNTL_H_ */
diff --git a/lib/libspl/include/os/freebsd/sys/Makefile.am b/lib/libspl/include/os/freebsd/sys/Makefile.am
index 6775522f5d..7a85460807 100644
--- a/lib/libspl/include/os/freebsd/sys/Makefile.am
+++ b/lib/libspl/include/os/freebsd/sys/Makefile.am
@@ -1,6 +1,7 @@
 libspldir = $(includedir)/libspl/sys
 libspl_HEADERS = \
 	byteorder.h \
+	fcntl.h \
 	file.h \
 	mnttab.h \
 	mount.h \
diff --git a/lib/libspl/include/os/freebsd/sys/fcntl.h b/lib/libspl/include/os/freebsd/sys/fcntl.h
new file mode 100644
index 0000000000..c8a37a1938
--- /dev/null
+++ b/lib/libspl/include/os/freebsd/sys/fcntl.h
@@ -0,0 +1,38 @@
+/*
+ * Copyright (c) 2021 iXsystems, Inc.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#ifndef _LIBSPL_SYS_FCNTL_H_
+#define	_LIBSPL_SYS_FCNTL_H_
+
+#include_next <sys/fcntl.h>
+
+#define	O_LARGEFILE	0
+#define	O_RSYNC		0
+
+#ifndef O_DSYNC
+#define	O_DSYNC		0
+#endif
+
+#endif	/* _LIBSPL_SYS_FCNTL_H_ */