diff --git a/releasetools/release.sh b/releasetools/release.sh
index 628b57a20..2539ee3e4 100755
--- a/releasetools/release.sh
+++ b/releasetools/release.sh
@@ -337,7 +337,7 @@ mount $TMPDISKUSR $RELEASEMNTDIR/usr || exit
 echo " * Copying files from staging to image"
 ##########################################################################
 synctree -f $RELEASEDIR $RELEASEMNTDIR > /dev/null || true
-expr `df -kP $TMPDISKUSR | tail -1 | awk '{ print $3 }'` - $extrakb >$RELEASEMNTDIR/.usrkb
+expr `/bin/df -kP $TMPDISKUSR | tail -1 | awk '{ print $3 }'` - $extrakb >$RELEASEMNTDIR/.usrkb
 
 echo " * Unmounting $TMPDISKUSR from $RELEASEMNTDIR/usr"
 umount $TMPDISKUSR || exit