Index: os-prober/linux-boot-probes/mounted/common/40grub2
===================================================================
--- os-prober.orig/linux-boot-probes/mounted/common/40grub2
+++ os-prober/linux-boot-probes/mounted/common/40grub2
@@ -16,7 +16,7 @@ found_item=0
 entry_result () {
 	if [ "x$type" = "xbtrfs" -a "$rootsv" = "$bootsv" ]; then
 		# trim off the leading subvol
-		kernelfile=$(echo "$kernel" | cut -d '/' -f 2- | cut -d '/' -f 2-)
+		kernelfile=$(echo "$kernel" | sed -e "s!^/${rootsv}/!!")
 	else
 		kernelfile=$kernel
 	fi