Index: stand/common/devopen.c
===================================================================
--- stand/common/devopen.c
+++ stand/common/devopen.c
@@ -29,8 +29,10 @@
 
 #include <stand.h>
 #include <string.h>
+#include <stdbool.h>
 
 #include "bootstrap.h"
+#include "disk.h"
 
 #ifdef LOADER_GELI_SUPPORT
 #include "geliboot.h"
@@ -41,6 +43,7 @@
 {
 	struct devdesc *dev;
 	int result;
+	bool is_open = false;
 
 	result = archsw.arch_getdev((void **)&dev, fname, file);
 	if (result)
@@ -49,11 +52,37 @@
 	/* point to device-specific data so that device open can use it */
 	f->f_dev = dev->d_dev;
 	f->f_devdata = dev;
-	result = dev->d_dev->dv_open(f, dev);
-	if (result != 0) {
-		f->f_devdata = NULL;
-		free(dev);
-		return (result);
+
+	/*
+	 * Traditinally the open of FREEBSD MBR slice means that we will
+	 * open the first BSD slice, if that does fail, only then we will
+	 * open the MBR slice.
+	 * To provide backwards compatibility, we need to check if there is
+	 * slice specified in device name, and if so, we will add partition
+	 * name 'a' and will try to open this updated name first.
+	 */
+	if (dev->d_dev->dv_type == DEVT_DISK) {
+		struct disk_devdesc *tdev;
+
+		tdev = (struct disk_devdesc *)dev;
+		if (tdev->d_partition == -1) {
+			tdev->d_partition = 0;
+			result = dev->d_dev->dv_open(f, dev);
+			if (result != 0) {
+				tdev->d_partition = -1;
+			} else {
+				is_open = true;
+			}
+		}
+	}
+
+	if (is_open == false) {
+		result = dev->d_dev->dv_open(f, dev);
+		if (result != 0) {
+			f->f_devdata = NULL;
+			free(dev);
+			return (result);
+		}
 	}
 
 #ifdef LOADER_GELI_SUPPORT