diff --git a/lib/libsysdecode/mkioctls b/lib/libsysdecode/mkioctls
index 05ae930888a1..19e898dcc85d 100644
--- a/lib/libsysdecode/mkioctls
+++ b/lib/libsysdecode/mkioctls
@@ -51,6 +51,7 @@ BEGIN {
 	print "#include <sys/param.h>"
 	print "#include <sys/devicestat.h>"
 	print "#include <sys/disklabel.h>"
+	print "#include <sys/mman.h>"
 	print "#include <sys/socket.h>"
 	print "#include <sys/time.h>"
 	print "#include <sys/tty.h>"