diff -Nru os-prober-1.70ubuntu3/debian/changelog os-prober-1.70ubuntu3.1/debian/changelog
--- os-prober-1.70ubuntu3/debian/changelog	2016-03-11 08:43:46.000000000 -0500
+++ os-prober-1.70ubuntu3.1/debian/changelog	2016-12-14 09:27:00.000000000 -0500
@@ -1,3 +1,11 @@
+os-prober (1.70ubuntu3.1) xenial; urgency=critical
+
+  * Fixing FS probes in os-probes/common/50mounted-tests (LP: #1579609). 
+    - debian/control: add Depends on grub-common (which ships grub-mount
+    and grub-probe) now that this is the only path to probing for filesystems.
+
+ -- Eric Desrochers <eric.desrochers@canonical.com>  Tue, 06 Dec 2016 10:05:22 -0500
+
 os-prober (1.70ubuntu3) xenial; urgency=low
 
   * Check for MSDOS extended partitions and skip any further tests which
diff -Nru os-prober-1.70ubuntu3/debian/control os-prober-1.70ubuntu3.1/debian/control
--- os-prober-1.70ubuntu3/debian/control	2015-11-20 05:19:42.000000000 -0500
+++ os-prober-1.70ubuntu3.1/debian/control	2016-12-14 09:25:21.000000000 -0500
@@ -24,7 +24,7 @@
 Architecture: any
 Section: utils
 Priority: extra
-Depends: ${shlibs:Depends}, ${misc:Depends}
+Depends: ${shlibs:Depends}, ${misc:Depends}, grub-common
 Description: utility to detect other OSes on a set of drives
  This package detects other OSes available on a system and outputs the
  results in a generic machine-readable format.
diff -Nru os-prober-1.70ubuntu3/os-probes/common/50mounted-tests os-prober-1.70ubuntu3.1/os-probes/common/50mounted-tests
--- os-prober-1.70ubuntu3/os-probes/common/50mounted-tests	2015-11-20 05:07:43.000000000 -0500
+++ os-prober-1.70ubuntu3.1/os-probes/common/50mounted-tests	2016-12-14 09:25:02.000000000 -0500
@@ -58,26 +58,8 @@
 		type=fuseblk
 	fi
 else
-	ro_partition "$partition"
-	for type in $types $delaytypes; do
-		if mount -o ro -t "$type" "$partition" "$tmpmnt" 2>/dev/null; then
-			debug "mounted as $type filesystem"
-			case "$type" in
-			    btrfs)
-				if [ -x "$tmpmnt/@/lib" ] && \
-				   ! mount --bind "$tmpmnt/@" "$tmpmnt"; then
-					warn "failed to mount btrfs subvolume @ on $partition"
-					if ! umount $tmpmnt; then
-						warn "failed to umount $tmpmnt"
-					fi
-					mounted=
-				fi
-				;;
-			esac	
-			mounted=1
-			break
-		fi
-	done
+	echo "Failed to probe for filesystem type" >&2
+	exit 1
 fi
 
 if [ "$mounted" ]; then