diff --git a/testnet/stacks-node/src/mockamoto.rs b/testnet/stacks-node/src/mockamoto.rs
index 9f11a872e..7b570b1e3 100644
--- a/testnet/stacks-node/src/mockamoto.rs
+++ b/testnet/stacks-node/src/mockamoto.rs
@@ -69,6 +69,7 @@ use stacks::net::atlas::{AtlasConfig, AtlasDB};
 use stacks::net::relay::Relayer;
 use stacks::net::stackerdb::StackerDBs;
 use stacks::util_lib::db::Error as DBError;
+use stacks::util_lib::signed_structured_data::{make_structured_data_domain, sign_structured_data};
 use stacks_common::address::{AddressHashMode, C32_ADDRESS_VERSION_TESTNET_SINGLESIG};
 use stacks_common::bitvec::BitVec;
 use stacks_common::codec::StacksMessageCodec;
@@ -81,7 +82,7 @@ use stacks_common::types::chainstate::{
 };
 use stacks_common::types::{PrivateKey, StacksEpochId};
 use stacks_common::util::hash::{to_hex, Hash160, MerkleTree, Sha512Trunc256Sum};
-use stacks_common::util::secp256k1::{MessageSignature, Secp256k1PublicKey};
+use stacks_common::util::secp256k1::{MessageSignature, Secp256k1PrivateKey, Secp256k1PublicKey};
 use stacks_common::util::vrf::{VRFPrivateKey, VRFProof, VRFPublicKey, VRF};
 
 use self::signer::SelfSigner;
@@ -832,8 +833,18 @@ impl MockamotoNode {
             Some(AddressHashMode::SerializeP2PKH),
         );
 
-        let mut signer_key = miner_nonce.to_be_bytes().to_vec();
-        signer_key.resize(33, 0);
+        let signer_sk = Secp256k1PrivateKey::from_seed(&miner_nonce.to_be_bytes());
+        let signer_key = Secp256k1PublicKey::from_private(&signer_sk).to_bytes_compressed();
+
+        let block_height = sortition_tip.block_height;
+        let reward_cycle = self
+            .sortdb
+            .pox_constants
+            .block_height_to_reward_cycle(self.sortdb.first_block_height, block_height)
+            .unwrap();
+
+        let signature =
+            make_signer_key_signature(&pox_address, &signer_sk, reward_cycle.into(), chain_id);
 
         let stack_stx_payload = if parent_chain_length < 2 {
             TransactionPayload::ContractCall(TransactionContractCall {
@@ -845,6 +856,7 @@ impl MockamotoNode {
                     pox_address.as_clarity_tuple().unwrap().into(),
                     ClarityValue::UInt(u128::from(parent_burn_height)),
                     ClarityValue::UInt(12),
+                    ClarityValue::buff_from(signature).unwrap(),
                     ClarityValue::buff_from(signer_key).unwrap(),
                 ],
             })
@@ -858,6 +870,7 @@ impl MockamotoNode {
                 function_args: vec![
                     ClarityValue::UInt(5),
                     pox_address.as_clarity_tuple().unwrap().into(),
+                    ClarityValue::buff_from(signature).unwrap(),
                     ClarityValue::buff_from(signer_key).unwrap(),
                 ],
             })
@@ -1019,3 +1032,28 @@ impl MockamotoNode {
         Ok(chain_length)
     }
 }
+
+fn make_signer_key_signature(
+    pox_addr: &PoxAddress,
+    signer_key: &StacksPrivateKey,
+    reward_cycle: u128,
+    chain_id: u32,
+) -> Vec<u8> {
+    let domain_tuple = make_structured_data_domain("pox-4-signer", "1.0.0", chain_id);
+
+    let data_tuple = clarity::vm::types::TupleData::from_data(vec![
+        (
+            "pox-addr".into(),
+            pox_addr.clone().as_clarity_tuple().unwrap().into(),
+        ),
+        (
+            "reward-cycle".into(),
+            clarity::vm::Value::UInt(reward_cycle),
+        ),
+    ])
+    .unwrap();
+
+    let signature = sign_structured_data(data_tuple.into(), domain_tuple, signer_key).unwrap();
+
+    signature.to_rsv()
+}