diff --git a/crates/blockifier/src/state/state_api.rs b/crates/blockifier/src/state/state_api.rs
index 38096fdcd8..5d3c308e2f 100644
--- a/crates/blockifier/src/state/state_api.rs
+++ b/crates/blockifier/src/state/state_api.rs
@@ -52,7 +52,7 @@ pub trait StateReader {
     // TODO(Dori, 1/9/2023): NEW_TOKEN_SUPPORT Determine fee token address based on tx version,
     //   once v3 is introduced.
     fn get_fee_token_balance(
-        &mut self,
+        &self,
         contract_address: ContractAddress,
         fee_token_address: ContractAddress,
     ) -> Result<(Felt, Felt), StateError> {
diff --git a/crates/blockifier/src/transaction/execution_flavors_test.rs b/crates/blockifier/src/transaction/execution_flavors_test.rs
index 82cb6e9f47..6f83a25d39 100644
--- a/crates/blockifier/src/transaction/execution_flavors_test.rs
+++ b/crates/blockifier/src/transaction/execution_flavors_test.rs
@@ -83,7 +83,7 @@ fn create_flavors_test_state(
 /// Returns the new balance.
 fn check_balance<S: StateReader>(
     current_balance: Felt,
-    state: &mut CachedState<S>,
+    state: &CachedState<S>,
     account_address: ContractAddress,
     chain_info: &ChainInfo,
     fee_type: &FeeType,
@@ -469,7 +469,7 @@ fn test_simulate_validate_charge_fee_mid_execution(
     );
     let current_balance = check_balance(
         current_balance,
-        &mut state,
+        &state,
         account_address,
         &block_context.chain_info,
         &fee_type,
@@ -520,7 +520,7 @@ fn test_simulate_validate_charge_fee_mid_execution(
     );
     let current_balance = check_balance(
         current_balance,
-        &mut state,
+        &state,
         account_address,
         chain_info,
         &fee_type,
@@ -564,7 +564,7 @@ fn test_simulate_validate_charge_fee_mid_execution(
         block_limit_fee,
         block_limit_fee,
     );
-    check_balance(current_balance, &mut state, account_address, chain_info, &fee_type, charge_fee);
+    check_balance(current_balance, &state, account_address, chain_info, &fee_type, charge_fee);
 }
 
 #[rstest]
@@ -654,7 +654,7 @@ fn test_simulate_validate_charge_fee_post_execution(
     );
     let current_balance = check_balance(
         current_balance,
-        &mut state,
+        &state,
         account_address,
         chain_info,
         &fee_type,
@@ -724,7 +724,7 @@ fn test_simulate_validate_charge_fee_post_execution(
     );
     check_balance(
         current_balance,
-        &mut state,
+        &state,
         account_address,
         chain_info,
         &fee_type,