diff --git a/specs/phase0/validator.md b/specs/phase0/validator.md
index 0e3af5b37d..c345508c16 100644
--- a/specs/phase0/validator.md
+++ b/specs/phase0/validator.md
@@ -597,12 +597,12 @@ each epoch. The `committee`, assigned `index`, and assigned `slot` for which the
 validator performs this role during an epoch are defined by
 `get_committee_assignment(state, epoch, validator_index)`.
 
-A validator should create and broadcast the `attestation` to the associated
-attestation subnet when either (a) the validator has received a valid block from
-the expected block proposer for the assigned `slot` or (b)
-`1 / INTERVALS_PER_SLOT` of the `slot` has transpired
-(`SECONDS_PER_SLOT / INTERVALS_PER_SLOT` seconds after the start of `slot`) --
-whichever comes _first_.
+A validator MUST create and broadcast the `attestation` to the associated
+attestation subnet immediately upon receiving a valid block from the expected
+block proposer for the assigned `slot`. If no valid block is received by
+`1 / INTERVALS_PER_SLOT` of the `slot` transpiring
+(`SECONDS_PER_SLOT / INTERVALS_PER_SLOT` seconds after the start of `slot`), the
+validator MUST create and broadcast the attestation at that time.
 
 *Note*: Although attestations during `GENESIS_EPOCH` do not count toward FFG
 finality, these initial attestations do give weight to the fork choice, are