[Dovecot] Sieve "header :value" test does not work

[Tom Hendrikx]

hi,

After following some examples and searching for sieve samples in this ml
history, I'm quite sure that the following sieve snippet should give no
surprises:

if header :value "ge" :comparator "i;ascii-numeric" "X-Header-Name"
"0.99" { /* do something */ }

However the Pigeonhole Sieve 0.2.3 on dovecot 2.0.14 gives me following
error:

test: line 3: error: unknown tagged argument ':value' for the header
test (reported only once at first occurence).
test: error: validation failed.

What obvious mistake am I failing to see here?

--
Tom