diff --git a/client/src/rpc_config.rs b/client/src/rpc_config.rs
index a33539423..1335b302d 100644
--- a/client/src/rpc_config.rs
+++ b/client/src/rpc_config.rs
@@ -1,6 +1,9 @@
 use crate::rpc_filter::RpcFilterType;
 use solana_account_decoder::{UiAccountEncoding, UiDataSliceConfig};
-use solana_sdk::{clock::Epoch, commitment_config::CommitmentConfig};
+use solana_sdk::{
+    clock::Epoch,
+    commitment_config::{CommitmentConfig, CommitmentLevel},
+};
 
 #[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
 #[serde(rename_all = "camelCase")]
@@ -11,14 +14,17 @@ pub struct RpcSignatureStatusConfig {
 #[derive(Debug, Default, Clone, Copy, PartialEq, Serialize, Deserialize)]
 #[serde(rename_all = "camelCase")]
 pub struct RpcSendTransactionConfig {
+    #[serde(default)]
     pub skip_preflight: bool,
-    pub preflight_commitment: Option<CommitmentConfig>,
+    pub preflight_commitment: Option<CommitmentLevel>,
 }
 
 #[derive(Debug, Default, Clone, PartialEq, Serialize, Deserialize)]
 #[serde(rename_all = "camelCase")]
 pub struct RpcSimulateTransactionConfig {
+    #[serde(default)]
     pub sig_verify: bool,
+    #[serde(flatten)]
     pub commitment: Option<CommitmentConfig>,
 }
 
diff --git a/core/src/rpc.rs b/core/src/rpc.rs
index 69986179e..23e072556 100644
--- a/core/src/rpc.rs
+++ b/core/src/rpc.rs
@@ -2176,7 +2176,10 @@ impl RpcSol for RpcSolImpl {
                 .into());
             }
 
-            let preflight_bank = &*meta.bank(config.preflight_commitment);
+            let preflight_commitment = config
+                .preflight_commitment
+                .map(|commitment| CommitmentConfig { commitment });
+            let preflight_bank = &*meta.bank(preflight_commitment);
             if let (Err(err), _log_output) =
                 preflight_bank.simulate_transaction(transaction.clone())
             {
diff --git a/docs/src/apps/jsonrpc-api.md b/docs/src/apps/jsonrpc-api.md
index a454bafe7..4ba6d8f4d 100644
--- a/docs/src/apps/jsonrpc-api.md
+++ b/docs/src/apps/jsonrpc-api.md
@@ -111,10 +111,10 @@ Requests can be sent in batches by sending an array of JSON-RPC request objects
 Solana nodes choose which bank state to query based on a commitment requirement
 set by the client. Clients may specify either:
 
-- `{"commitment":"max"}` - the node will query the most recent bank confirmed by the cluster as having reached `MAX_LOCKOUT_HISTORY` confirmations
-- `{"commitment":"root"}` - the node will query the most recent bank having reached `MAX_LOCKOUT_HISTORY` confirmations on this node
-- `{"commitment":"single"}` - the node will query the most recent bank having reached 1 confirmation
-- `{"commitment":"recent"}` - the node will query its most recent bank
+- `"max"` - the node will query the most recent bank confirmed by the cluster as having reached `MAX_LOCKOUT_HISTORY` confirmations
+- `"root"` - the node will query the most recent bank having reached `MAX_LOCKOUT_HISTORY` confirmations on this node
+- `"single"` - the node will query the most recent bank having reached 1 confirmation
+- `"recent"` - the node will query its most recent bank
 
 The commitment parameter should be included as the last element in the `params` array:
 
@@ -124,7 +124,7 @@ curl -X POST -H "Content-Type: application/json" -d '{"jsonrpc":"2.0", "id":1, "
 
 #### Default:
 
-If commitment configuration is not provided, the node will default to `"commitment":"max"`
+If commitment configuration is not provided, the node will default to `"max"` commitment
 
 Only methods that query bank state accept the commitment parameter. They are indicated in the API Reference below.
 
@@ -1397,7 +1397,7 @@ Before submitting, the following preflight checks are performed:
 - `<string>` - fully-signed Transaction, as base-58 encoded string
 - `<object>` - (optional) Configuration object containing the following field:
   - `skipPreflight: <bool>` - if true, skip the preflight transaction checks (default: false)
-  - `preflightCommitment: <object>` - (optional) [Commitment](jsonrpc-api.md#configuring-state-commitment) level to use for preflight (default: max).
+  - `preflightCommitment: <string>` - (optional) [Commitment](jsonrpc-api.md#configuring-state-commitment) level to use for preflight (default: `"max"`).
 
 #### Results:
 
@@ -1422,7 +1422,7 @@ Simulate sending a transaction
 - `<string>` - Transaction, as base-58 encoded string. The transaction must have a valid blockhash, but is not required to be signed.
 - `<object>` - (optional) Configuration object containing the following field:
   - `sigVerify: <bool>` - if true the transaction signatures will be verified (default: false)
-  - `commitment: <object>` - (optional) [Commitment](jsonrpc-api.md#configuring-state-commitment) level to simulate the transaction at (default: max).
+  - `commitment: <string>` - (optional) [Commitment](jsonrpc-api.md#configuring-state-commitment) level to simulate the transaction at (default: `"max"`).
 
 #### Results: