diff --git a/sys/vm/vm_mmap.c b/sys/vm/vm_mmap.c
index 2b99e3653df..c8d25ee3a30 100644
--- a/sys/vm/vm_mmap.c
+++ b/sys/vm/vm_mmap.c
@@ -64,6 +64,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/mount.h>
 #include <sys/conf.h>
 #include <sys/stat.h>
+#include <sys/sysent.h>
 #include <sys/vmmeter.h>
 #include <sys/sysctl.h>
 
@@ -229,7 +230,8 @@ mmap(td, uap)
 
 	fp = NULL;
 	/* make sure mapping fits into numeric range etc */
-	if (uap->len == 0 ||
+	if ((uap->len == 0 && !SV_CURPROC_FLAG(SV_AOUT) &&
+	     curproc->p_osrel >= 800104) ||
 	    ((flags & MAP_ANON) && uap->fd != -1))
 		return (EINVAL);