diff --git a/specs/core/0_beacon-chain.md b/specs/core/0_beacon-chain.md
index 049e513b6..48425183c 100644
--- a/specs/core/0_beacon-chain.md
+++ b/specs/core/0_beacon-chain.md
@@ -419,7 +419,7 @@ Unless otherwise indicated, code appearing in `this style` is to be interpreted
 
 #### `BeaconBlockBody`
 
-`ProofOfCustodySeedChange`, `ProofOfCustodyChallenge`, and `ProofOfCustodyResponse` will be defined in phase 1; for now put dummy classes as these lists will remain empty throughout phase 0.
+`ProofOfCustodySeedChange`, `ProofOfCustodyChallenge`, and `ProofOfCustodyResponse` will be defined in phase 1; for now, put dummy classes as these lists will remain empty throughout phase 0.
 
 ```python
 {