diff --git a/install.sh b/install.sh
index cb479e30dd..90b15423b9 100755
--- a/install.sh
+++ b/install.sh
@@ -473,7 +473,7 @@ do_unmount() {
     while read ignore mount ignore; do
         MOUNTS="$mount\n$MOUNTS"
     done </proc/self/mounts
-    MOUNTS=$(printf $MOUNTS | sort -r -)
+    MOUNTS=$(printf $MOUNTS | grep "^$1" | sort -r)
     if [ -n "${MOUNTS}" ]; then
         umount ${MOUNTS}
     fi