diff --git a/spec/index.md b/spec/index.md
index b7e486d5..5bf31d4a 100644
--- a/spec/index.md
+++ b/spec/index.md
@@ -2447,9 +2447,9 @@ The encoding of the signature depends on the key ID's `algorithm`:
 
 This call requires that a Schnorr key with ID `key_id` was generated by the IC and the signing functionality for that key was enabled. Otherwise, the call is rejected.
 
-This call accepts an optional auxiliary parameter `aux`. The auxiliary parameter type `schnorr_aux` is a variant. The only currently supported variant is `bip341` which allows passing a Merkle tree root hash, which is required to implement Taproot signatures as defined in [BIP341](https://github.com/bitcoin/bips/blob/master/bip-0341.mediawiki). The `bip341` variant is only allowed for `bip340secp256k1` signatures, and if provided the `merkle_root_hash` must be generated in accordance with BIP341's specification for `taproot_output_script`. Specifically it should be either an empty bytestring (for the `script == None` case) or else 32 bytes generated using the procedure documented as `taproot_tree_helper`. If no auxiliary parameter is provided, then `bip340secp256k1` signatures are generated in accordance with BIP340.
+This call accepts an optional auxiliary parameter `aux`. The auxiliary parameter type `schnorr_aux` is an enumeration. The only currently supported variant is `bip341` which allows passing a Merkle tree root hash, which is required to implement Taproot signatures as defined in [BIP341](https://github.com/bitcoin/bips/blob/master/bip-0341.mediawiki). The `bip341` variant is only allowed for `bip340secp256k1` signatures, and if provided the `merkle_root_hash` must be generated in accordance with BIP341's specification for `taproot_output_script`. Specifically it should be either an empty bytestring (for the `script == None` case) or else 32 bytes generated using the procedure documented as `taproot_tree_helper`. If no auxiliary parameter is provided, then `bip340secp256k1` signatures are generated in accordance with BIP340.
 
-On the Internet Computer, the tuple of the requested master key, the calling canister, and derivation path determines which private key that is used to generate the signature, and which public key is returned by `schnorr_public_key`.
+On the Internet Computer, the tuple of the requested master key, the calling canister, and derivation path determines which private key is used to generate the signature, and which public key is returned by `schnorr_public_key`.
 
 When using BIP341 signatures, the actual signature that is created will be relative to the Schnorr signature derived as described in BIP341's `taproot_sign_script`. The key returned by `schnorr_public_key` is the value identified in BIP341 as `internal_pubkey`.