conditionals in Makefiles

I am trying to make a block of my package Makefile conditional on the OPSYS, like so...

.if ${OPSYS} == "SunOS"
# do stuff....
.endif

...but when I bmake, it says ''Malformed conditional (${OPSYS} == "SunOS")'' and ''Need an operator''.  However, plenty of other package Makefiles are doing this, so I must be missing something.


Thanks,
Tim

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