diff --git a/chain.go b/chain.go
index 9e580824..0b18faa5 100644
--- a/chain.go
+++ b/chain.go
@@ -96,8 +96,13 @@ func (r FutureGetBlockResult) Receive() (*btcutil.Block, error) {
 //
 // See GetBlock for the blocking version and more details.
 func (c *Client) GetBlockAsync(blockHash *btcwire.ShaHash) FutureGetBlockResult {
+	hash := ""
+	if blockHash != nil {
+		hash = blockHash.String()
+	}
+
 	id := c.NextID()
-	cmd, err := btcjson.NewGetBlockCmd(id, blockHash.String(), false)
+	cmd, err := btcjson.NewGetBlockCmd(id, hash, false)
 	if err != nil {
 		return newFutureError(err)
 	}
@@ -141,9 +146,13 @@ func (r FutureGetBlockVerboseResult) Receive() (*btcjson.BlockResult, error) {
 //
 // See GetBlockVerbose for the blocking version and more details.
 func (c *Client) GetBlockVerboseAsync(blockHash *btcwire.ShaHash, verboseTx bool) FutureGetBlockVerboseResult {
+	hash := ""
+	if blockHash != nil {
+		hash = blockHash.String()
+	}
+
 	id := c.NextID()
-	cmd, err := btcjson.NewGetBlockCmd(id, blockHash.String(), true,
-		verboseTx)
+	cmd, err := btcjson.NewGetBlockCmd(id, hash, true, verboseTx)
 	if err != nil {
 		return newFutureError(err)
 	}
diff --git a/mining.go b/mining.go
index 924c3caf..8336d239 100644
--- a/mining.go
+++ b/mining.go
@@ -384,13 +384,17 @@ func (r FutureSubmitBlockResult) Receive() error {
 //
 // See SubmitBlock for the blocking version and more details.
 func (c *Client) SubmitBlockAsync(block *btcutil.Block, options *btcjson.SubmitBlockOptions) FutureSubmitBlockResult {
-	id := c.NextID()
-	blockBytes, err := block.Bytes()
-	if err != nil {
-		return newFutureError(err)
+	blockHex := ""
+	if block != nil {
+		blockBytes, err := block.Bytes()
+		if err != nil {
+			return newFutureError(err)
+		}
+
+		blockHex = hex.EncodeToString(blockBytes)
 	}
 
-	blockHex := hex.EncodeToString(blockBytes)
+	id := c.NextID()
 	cmd, err := btcjson.NewSubmitBlockCmd(id, blockHex, options)
 	if err != nil {
 		return newFutureError(err)
diff --git a/rawtransactions.go b/rawtransactions.go
index a1ef6cf8..d1657ff9 100644
--- a/rawtransactions.go
+++ b/rawtransactions.go
@@ -95,8 +95,13 @@ func (r FutureGetRawTransactionResult) Receive() (*btcutil.Tx, error) {
 //
 // See GetRawTransaction for the blocking version and more details.
 func (c *Client) GetRawTransactionAsync(txHash *btcwire.ShaHash) FutureGetRawTransactionResult {
+	hash := ""
+	if txHash != nil {
+		hash = txHash.String()
+	}
+
 	id := c.NextID()
-	cmd, err := btcjson.NewGetRawTransactionCmd(id, txHash.String(), 0)
+	cmd, err := btcjson.NewGetRawTransactionCmd(id, hash, 0)
 	if err != nil {
 		return newFutureError(err)
 	}
@@ -141,8 +146,13 @@ func (r FutureGetRawTransactionVerboseResult) Receive() (*btcjson.TxRawResult, e
 //
 // See GetRawTransactionVerbose for the blocking version and more details.
 func (c *Client) GetRawTransactionVerboseAsync(txHash *btcwire.ShaHash) FutureGetRawTransactionVerboseResult {
+	hash := ""
+	if txHash != nil {
+		hash = txHash.String()
+	}
+
 	id := c.NextID()
-	cmd, err := btcjson.NewGetRawTransactionCmd(id, txHash.String(), 1)
+	cmd, err := btcjson.NewGetRawTransactionCmd(id, hash, 1)
 	if err != nil {
 		return newFutureError(err)
 	}
@@ -294,12 +304,15 @@ func (r FutureSendRawTransactionResult) Receive() (*btcwire.ShaHash, error) {
 //
 // See SendRawTransaction for the blocking version and more details.
 func (c *Client) SendRawTransactionAsync(tx *btcwire.MsgTx, allowHighFees bool) FutureSendRawTransactionResult {
-	// Serialize the transaction and convert to hex string.
-	buf := bytes.NewBuffer(make([]byte, 0, tx.SerializeSize()))
-	if err := tx.Serialize(buf); err != nil {
-		return newFutureError(err)
+	txHex := ""
+	if tx != nil {
+		// Serialize the transaction and convert to hex string.
+		buf := bytes.NewBuffer(make([]byte, 0, tx.SerializeSize()))
+		if err := tx.Serialize(buf); err != nil {
+			return newFutureError(err)
+		}
+		txHex = hex.EncodeToString(buf.Bytes())
 	}
-	txHex := hex.EncodeToString(buf.Bytes())
 
 	id := c.NextID()
 	cmd, err := btcjson.NewSendRawTransactionCmd(id, txHex, allowHighFees)
@@ -357,12 +370,15 @@ func (r FutureSignRawTransactionResult) Receive() (*btcwire.MsgTx, bool, error)
 //
 // See SignRawTransaction for the blocking version and more details.
 func (c *Client) SignRawTransactionAsync(tx *btcwire.MsgTx) FutureSignRawTransactionResult {
-	// Serialize the transaction and convert to hex string.
-	buf := bytes.NewBuffer(make([]byte, 0, tx.SerializeSize()))
-	if err := tx.Serialize(buf); err != nil {
-		return newFutureError(err)
+	txHex := ""
+	if tx != nil {
+		// Serialize the transaction and convert to hex string.
+		buf := bytes.NewBuffer(make([]byte, 0, tx.SerializeSize()))
+		if err := tx.Serialize(buf); err != nil {
+			return newFutureError(err)
+		}
+		txHex = hex.EncodeToString(buf.Bytes())
 	}
-	txHex := hex.EncodeToString(buf.Bytes())
 
 	id := c.NextID()
 	cmd, err := btcjson.NewSignRawTransactionCmd(id, txHex)
@@ -390,12 +406,15 @@ func (c *Client) SignRawTransaction(tx *btcwire.MsgTx) (*btcwire.MsgTx, bool, er
 //
 // See SignRawTransaction2 for the blocking version and more details.
 func (c *Client) SignRawTransaction2Async(tx *btcwire.MsgTx, inputs []btcjson.RawTxInput) FutureSignRawTransactionResult {
-	// Serialize the transaction and convert to hex string.
-	buf := bytes.NewBuffer(make([]byte, 0, tx.SerializeSize()))
-	if err := tx.Serialize(buf); err != nil {
-		return newFutureError(err)
+	txHex := ""
+	if tx != nil {
+		// Serialize the transaction and convert to hex string.
+		buf := bytes.NewBuffer(make([]byte, 0, tx.SerializeSize()))
+		if err := tx.Serialize(buf); err != nil {
+			return newFutureError(err)
+		}
+		txHex = hex.EncodeToString(buf.Bytes())
 	}
-	txHex := hex.EncodeToString(buf.Bytes())
 
 	id := c.NextID()
 	cmd, err := btcjson.NewSignRawTransactionCmd(id, txHex, inputs)
@@ -429,12 +448,15 @@ func (c *Client) SignRawTransaction3Async(tx *btcwire.MsgTx,
 	inputs []btcjson.RawTxInput,
 	privKeysWIF []string) FutureSignRawTransactionResult {
 
-	// Serialize the transaction and convert to hex string.
-	buf := bytes.NewBuffer(make([]byte, 0, tx.SerializeSize()))
-	if err := tx.Serialize(buf); err != nil {
-		return newFutureError(err)
+	txHex := ""
+	if tx != nil {
+		// Serialize the transaction and convert to hex string.
+		buf := bytes.NewBuffer(make([]byte, 0, tx.SerializeSize()))
+		if err := tx.Serialize(buf); err != nil {
+			return newFutureError(err)
+		}
+		txHex = hex.EncodeToString(buf.Bytes())
 	}
-	txHex := hex.EncodeToString(buf.Bytes())
 
 	id := c.NextID()
 	cmd, err := btcjson.NewSignRawTransactionCmd(id, txHex, inputs,
@@ -479,12 +501,15 @@ func (c *Client) SignRawTransaction4Async(tx *btcwire.MsgTx,
 	inputs []btcjson.RawTxInput, privKeysWIF []string,
 	hashType SigHashType) FutureSignRawTransactionResult {
 
-	// Serialize the transaction and convert to hex string.
-	buf := bytes.NewBuffer(make([]byte, 0, tx.SerializeSize()))
-	if err := tx.Serialize(buf); err != nil {
-		return newFutureError(err)
+	txHex := ""
+	if tx != nil {
+		// Serialize the transaction and convert to hex string.
+		buf := bytes.NewBuffer(make([]byte, 0, tx.SerializeSize()))
+		if err := tx.Serialize(buf); err != nil {
+			return newFutureError(err)
+		}
+		txHex = hex.EncodeToString(buf.Bytes())
 	}
-	txHex := hex.EncodeToString(buf.Bytes())
 
 	id := c.NextID()
 	cmd, err := btcjson.NewSignRawTransactionCmd(id, txHex, inputs,
diff --git a/wallet.go b/wallet.go
index 486fc7be..47f812e6 100644
--- a/wallet.go
+++ b/wallet.go
@@ -44,8 +44,13 @@ func (r FutureGetTransactionResult) Receive() (*btcjson.GetTransactionResult, er
 //
 // See GetTransaction for the blocking version and more details.
 func (c *Client) GetTransactionAsync(txHash *btcwire.ShaHash) FutureGetTransactionResult {
+	hash := ""
+	if txHash != nil {
+		hash = txHash.String()
+	}
+
 	id := c.NextID()
-	cmd, err := btcjson.NewGetTransactionCmd(id, txHash.String())
+	cmd, err := btcjson.NewGetTransactionCmd(id, hash)
 	if err != nil {
 		return newFutureError(err)
 	}
@@ -316,6 +321,7 @@ func (c *Client) ListSinceBlockAsync(blockHash *btcwire.ShaHash) FutureListSince
 	if blockHash != nil {
 		hash = blockHash.String()
 	}
+
 	id := c.NextID()
 	cmd, err := btcjson.NewListSinceBlockCmd(id, hash)
 	if err != nil {
@@ -344,6 +350,7 @@ func (c *Client) ListSinceBlockMinConfAsync(blockHash *btcwire.ShaHash, minConfi
 	if blockHash != nil {
 		hash = blockHash.String()
 	}
+
 	id := c.NextID()
 	cmd, err := btcjson.NewListSinceBlockCmd(id, hash, minConfirms)
 	if err != nil {