.ONESHELL causes quoting in .SHELLFLAGS to not work as expected

[Britton Kerin]

$ cat Makefile
.ONESHELL:
SHELL = /usr/bin/perl
.SHELLFLAGS = -w -E 'use warnings FATAL => "all";' -E
all:
        print 'it works'
$ make all
print 'it works'
Can't find string terminator "'" anywhere before EOF at -e line 1.
make: *** [Makefile:5: all] Error 255
$

Without .ONESHELL: the above works as expected.

Britton