diff --git a/scripts/Build-Target b/scripts/Build-Target
index 0e5006c6b..c573ff7d3 100755
--- a/scripts/Build-Target
+++ b/scripts/Build-Target
@@ -355,6 +355,22 @@ pkgloop_action() {
 	$cmd_buildpkg
 }
 
+# Try to umount any directories mounted by Build-Pkg -chroot
+# if we are the last process using them.
+#
+umount_chroot() {
+	exec 201> /dev/null
+	if [ -z "$( fuser "${build_logs}/*.log" )" ]; then
+		umount -d -f    $build_rock/{loop,config,download} 2> /dev/null
+		umount -d -f -l $build_rock/{loop,config,download} 2> /dev/null
+		umount -d -f    $build_root/proc 2> /dev/null
+		umount -d -f -l $build_root/proc 2> /dev/null
+	fi
+}
+
+# must trap outside the group command
+trap 'umount_chroot' EXIT
+
 {
 	ln -sf build_target_$$.log ${build_logs}/build_target.log
 	./scripts/Build-Tools -1 -cfg $config