Index: os-prober/os-probes/common/50mounted-tests
===================================================================
--- os-prober.orig/os-probes/common/50mounted-tests
+++ os-prober/os-probes/common/50mounted-tests
@@ -115,6 +115,7 @@ if [ "$types" = btrfs ]; then
         subvols=$(btrfs subvolume list -a "$tmpmnt" | cut -d ' ' -f 9 | sed -e s!^\<FS_TREE\>/!!)
         rosubvols=$(btrfs subvolume list -r -a "$tmpmnt" | cut -d ' ' -f 9 | sed -e s!^\<FS_TREE\>/!!)
         sssubvols=$(btrfs subvolume list -s -a "$tmpmnt" | cut -d ' ' -f 14 | sed -e s!^\<FS_TREE\>/!!)
+        defaultvol=$(btrfs subvolume get-default "$tmpmnt" | cut -d ' ' -f 9)
         if ! umount "$tmpmnt"; then
             warn "failed to umount btrfs volume on $tmpmnt"
             rmdir "$tmpmnt" || true
@@ -157,11 +157,13 @@ if [ "$types" = btrfs ]; then
 		found=
                 for subvol in $subvols; do
 			debug "begin btrfs processing for $UUID subvol=$subvol"
-			if echo "$rosubvols" | grep -q -x "$subvol"; then
-				continue
-			fi
-			if echo "$sssubvols" | grep -q -x "$subvol"; then
-				continue
+	                if [ "$subvol" != "$defaultvol" ]; then
+				if echo "$rosubvols" | grep -q -x "$subvol"; then
+					continue
+				fi
+				if echo "$sssubvols" | grep -q -x "$subvol"; then
+					continue
+				fi
 			fi
 			mounted=
 			mpoint="$(grep btrfs /proc/self/mountinfo | grep "$partition " | grep "/$subvol " | cut -d ' ' -f 5)"