diff --git a/specs/core/0_beacon-chain.md b/specs/core/0_beacon-chain.md
index 30fb27c19..6f3a02976 100644
--- a/specs/core/0_beacon-chain.md
+++ b/specs/core/0_beacon-chain.md
@@ -1058,7 +1058,7 @@ def is_surround_vote(attestation_data_1: AttestationData,
                      attestation_data_2: AttestationData) -> bool
     """
     Assumes ``attestation_data_1`` is distinct from ``attestation_data_2``.
-    Returns True if the provided ``AttestationData`` is slashable
+    Returns True if the provided ``AttestationData`` are slashable
     due to a 'surround vote'.
     Note: parameter order matters as this function only checks
     that ``attestation_data_1`` surrounds ``attestation_data_2``.