diff --git a/program/src/close.rs b/program/src/close.rs
index 2363e57..4844200 100644
--- a/program/src/close.rs
+++ b/program/src/close.rs
@@ -46,8 +46,8 @@ pub fn process_close(accounts: &[AccountInfo<'_>], _data: &[u8]) -> ProgramResul
     if block.best_hash_miner != Pubkey::default() {
         // Load winning miner.
         let miner = miner_info
-            .has_address(&block.best_hash_miner)?
-            .as_account_mut::<Miner>(&ore_api::ID)?;
+            .as_account_mut::<Miner>(&ore_api::ID)?
+            .assert_mut(|m| m.authority == block.best_hash_miner)?;
 
         // Update stats.
         miner.total_rewards += block.reward;
diff --git a/program/src/mine.rs b/program/src/mine.rs
index 8e2f7ac..94919cb 100644
--- a/program/src/mine.rs
+++ b/program/src/mine.rs
@@ -37,7 +37,7 @@ pub fn process_mine(accounts: &[AccountInfo<'_>], data: &[u8]) -> ProgramResult
     // If hash is best hash, update best hash.
     if h < block.best_hash {
         block.best_hash = h;
-        block.best_hash_miner = *miner_info.key;
+        block.best_hash_miner = miner.authority;
     }
 
     // Only allow miners to submit 1 hash per block.