diff --git a/src/psbt.js b/src/psbt.js
index b9ed061..4a6306f 100644
--- a/src/psbt.js
+++ b/src/psbt.js
@@ -11,6 +11,39 @@ const bscript = require('./script');
 const transaction_1 = require('./transaction');
 const varuint = require('varuint-bitcoin');
 class Psbt extends bip174_1.Psbt {
+  static fromTransaction(txBuf) {
+    const tx = transaction_1.Transaction.fromBuffer(txBuf);
+    const psbt = new this();
+    psbt.__TX = tx;
+    let inputCount = tx.ins.length;
+    let outputCount = tx.outs.length;
+    while (inputCount > 0) {
+      psbt.inputs.push({
+        keyVals: [],
+      });
+      inputCount--;
+    }
+    while (outputCount > 0) {
+      psbt.outputs.push({
+        keyVals: [],
+      });
+      outputCount--;
+    }
+    return psbt;
+  }
+  static fromBuffer(buffer) {
+    let tx;
+    const txCountGetter = txBuf => {
+      tx = transaction_1.Transaction.fromBuffer(txBuf);
+      return {
+        inputCount: tx.ins.length,
+        outputCount: tx.outs.length,
+      };
+    };
+    const psbt = super.fromBuffer(buffer, txCountGetter);
+    psbt.__TX = tx;
+    return psbt;
+  }
   constructor(opts = {}) {
     super();
     // set defaults
@@ -40,7 +73,7 @@ class Psbt extends bip174_1.Psbt {
         enumerable,
         writable,
       });
-    dpew(this, '__TX', false, false);
+    dpew(this, '__TX', false, true);
     dpew(this, '__TX_BUF_CACHE', false, true);
     dpew(this, 'opts', false, true);
   }
@@ -112,7 +145,7 @@ class Psbt extends bip174_1.Psbt {
   }
   extractTransaction() {
     if (!this.inputs.every(isFinalized)) throw new Error('Not finalized');
-    const tx = transaction_1.Transaction.fromBuffer(this.globalMap.unsignedTx);
+    const tx = this.__TX.clone();
     this.inputs.forEach((input, idx) => {
       if (input.finalScriptSig) tx.ins[idx].script = input.finalScriptSig;
       if (input.finalScriptWitness) {
@@ -138,7 +171,7 @@ class Psbt extends bip174_1.Psbt {
     const { script, isP2SH, isP2WSH, isSegwit } = getScriptFromInput(
       inputIndex,
       input,
-      this.globalMap.unsignedTx,
+      this.__TX,
     );
     if (!script) return false;
     const scriptType = classifyScript(script);
@@ -166,7 +199,7 @@ class Psbt extends bip174_1.Psbt {
       this.inputs,
       inputIndex,
       keyPair.publicKey,
-      this.globalMap.unsignedTx,
+      this.__TX,
     );
     const partialSig = {
       pubkey: keyPair.publicKey,
@@ -182,7 +215,7 @@ class Psbt extends bip174_1.Psbt {
         this.inputs,
         inputIndex,
         keyPair.publicKey,
-        this.globalMap.unsignedTx,
+        this.__TX,
       );
       Promise.resolve(keyPair.sign(hash)).then(signature => {
         const partialSig = {
@@ -202,9 +235,13 @@ const DEFAULT_OPTS = {
 function isFinalized(input) {
   return !!input.finalScriptSig || !!input.finalScriptWitness;
 }
-function getHashAndSighashType(inputs, inputIndex, pubkey, txBuf) {
+function getHashAndSighashType(inputs, inputIndex, pubkey, unsignedTx) {
   const input = utils_1.checkForInput(inputs, inputIndex);
-  const { hash, sighashType, script } = getHashForSig(inputIndex, input, txBuf);
+  const { hash, sighashType, script } = getHashForSig(
+    inputIndex,
+    input,
+    unsignedTx,
+  );
   checkScriptForPubkey(pubkey, script);
   return {
     hash,
@@ -322,8 +359,7 @@ function checkScriptForPubkey(pubkey, script) {
     );
   }
 }
-const getHashForSig = (inputIndex, input, txBuf) => {
-  const unsignedTx = transaction_1.Transaction.fromBuffer(txBuf);
+const getHashForSig = (inputIndex, input, unsignedTx) => {
   const sighashType =
     input.sighashType || transaction_1.Transaction.SIGHASH_ALL;
   let hash;
@@ -442,7 +478,7 @@ const classifyScript = script => {
   if (isP2PK(script)) return 'pubkey';
   return 'nonstandard';
 };
-function getScriptFromInput(inputIndex, input, _unsignedTx) {
+function getScriptFromInput(inputIndex, input, unsignedTx) {
   const res = {
     script: null,
     isSegwit: false,
@@ -454,7 +490,6 @@ function getScriptFromInput(inputIndex, input, _unsignedTx) {
       res.isP2SH = true;
       res.script = input.redeemScript;
     } else {
-      const unsignedTx = transaction_1.Transaction.fromBuffer(_unsignedTx);
       const nonWitnessUtxoTx = transaction_1.Transaction.fromBuffer(
         input.nonWitnessUtxo,
       );
diff --git a/ts_src/psbt.ts b/ts_src/psbt.ts
index 2c36130..0aee319 100644
--- a/ts_src/psbt.ts
+++ b/ts_src/psbt.ts
@@ -17,6 +17,50 @@ import { Transaction } from './transaction';
 const varuint = require('varuint-bitcoin');
 
 export class Psbt extends PsbtBase {
+  static fromTransaction<T extends typeof PsbtBase>(
+    this: T,
+    txBuf: Buffer,
+  ): InstanceType<T> {
+    const tx = Transaction.fromBuffer(txBuf);
+    const psbt = new this() as Psbt;
+    psbt.__TX = tx;
+    let inputCount = tx.ins.length;
+    let outputCount = tx.outs.length;
+    while (inputCount > 0) {
+      psbt.inputs.push({
+        keyVals: [],
+      });
+      inputCount--;
+    }
+    while (outputCount > 0) {
+      psbt.outputs.push({
+        keyVals: [],
+      });
+      outputCount--;
+    }
+    return psbt as InstanceType<T>;
+  }
+  static fromBuffer<T extends typeof PsbtBase>(
+    this: T,
+    buffer: Buffer,
+  ): InstanceType<T> {
+    let tx: Transaction | undefined;
+    const txCountGetter = (
+      txBuf: Buffer,
+    ): {
+      inputCount: number;
+      outputCount: number;
+    } => {
+      tx = Transaction.fromBuffer(txBuf);
+      return {
+        inputCount: tx.ins.length,
+        outputCount: tx.outs.length,
+      };
+    };
+    const psbt = super.fromBuffer(buffer, txCountGetter) as Psbt;
+    psbt.__TX = tx!;
+    return psbt as InstanceType<T>;
+  }
   private __TX: Transaction;
   private __TX_BUF_CACHE?: Buffer;
   private opts: PsbtOpts;
@@ -56,7 +100,7 @@ export class Psbt extends PsbtBase {
         enumerable,
         writable,
       });
-    dpew(this, '__TX', false, false);
+    dpew(this, '__TX', false, true);
     dpew(this, '__TX_BUF_CACHE', false, true);
     dpew(this, 'opts', false, true);
   }
@@ -138,7 +182,7 @@ export class Psbt extends PsbtBase {
 
   extractTransaction(): Transaction {
     if (!this.inputs.every(isFinalized)) throw new Error('Not finalized');
-    const tx = Transaction.fromBuffer(this.globalMap.unsignedTx!);
+    const tx = this.__TX.clone();
     this.inputs.forEach((input, idx) => {
       if (input.finalScriptSig) tx.ins[idx].script = input.finalScriptSig;
       if (input.finalScriptWitness) {
@@ -169,7 +213,7 @@ export class Psbt extends PsbtBase {
     const { script, isP2SH, isP2WSH, isSegwit } = getScriptFromInput(
       inputIndex,
       input,
-      this.globalMap.unsignedTx!,
+      this.__TX,
     );
     if (!script) return false;
 
@@ -195,14 +239,14 @@ export class Psbt extends PsbtBase {
     return true;
   }
 
-  signInput(inputIndex: number, keyPair: Signer): Psbt {
+  signInput(inputIndex: number, keyPair: Signer): this {
     if (!keyPair || !keyPair.publicKey)
       throw new Error('Need Signer to sign input');
     const { hash, sighashType } = getHashAndSighashType(
       this.inputs,
       inputIndex,
       keyPair.publicKey,
-      this.globalMap.unsignedTx!,
+      this.__TX,
     );
 
     const partialSig = {
@@ -222,7 +266,7 @@ export class Psbt extends PsbtBase {
           this.inputs,
           inputIndex,
           keyPair.publicKey,
-          this.globalMap.unsignedTx!,
+          this.__TX,
         );
 
         Promise.resolve(keyPair.sign(hash)).then(signature => {
@@ -269,13 +313,17 @@ function getHashAndSighashType(
   inputs: PsbtInput[],
   inputIndex: number,
   pubkey: Buffer,
-  txBuf: Buffer,
+  unsignedTx: Transaction,
 ): {
   hash: Buffer;
   sighashType: number;
 } {
   const input = checkForInput(inputs, inputIndex);
-  const { hash, sighashType, script } = getHashForSig(inputIndex, input, txBuf);
+  const { hash, sighashType, script } = getHashForSig(
+    inputIndex,
+    input,
+    unsignedTx,
+  );
   checkScriptForPubkey(pubkey, script);
   return {
     hash,
@@ -424,9 +472,8 @@ interface HashForSigData {
 const getHashForSig = (
   inputIndex: number,
   input: PsbtInput,
-  txBuf: Buffer,
+  unsignedTx: Transaction,
 ): HashForSigData => {
-  const unsignedTx = Transaction.fromBuffer(txBuf);
   const sighashType = input.sighashType || Transaction.SIGHASH_ALL;
   let hash: Buffer;
   let script: Buffer;
@@ -571,7 +618,7 @@ interface GetScriptReturn {
 function getScriptFromInput(
   inputIndex: number,
   input: PsbtInput,
-  _unsignedTx: Buffer,
+  unsignedTx: Transaction,
 ): GetScriptReturn {
   const res: GetScriptReturn = {
     script: null,
@@ -584,7 +631,6 @@ function getScriptFromInput(
       res.isP2SH = true;
       res.script = input.redeemScript;
     } else {
-      const unsignedTx = Transaction.fromBuffer(_unsignedTx);
       const nonWitnessUtxoTx = Transaction.fromBuffer(input.nonWitnessUtxo);
       const prevoutIndex = unsignedTx.ins[inputIndex].index;
       res.script = nonWitnessUtxoTx.outs[prevoutIndex].script;
diff --git a/types/psbt.d.ts b/types/psbt.d.ts
index 213c31b..a203854 100644
--- a/types/psbt.d.ts
+++ b/types/psbt.d.ts
@@ -1,9 +1,12 @@
+/// <reference types="node" />
 import { Psbt as PsbtBase } from 'bip174';
 import { TransactionInput, TransactionOutput } from 'bip174/src/lib/interfaces';
 import { Signer, SignerAsync } from './ecpair';
 import { Network } from './networks';
 import { Transaction } from './transaction';
 export declare class Psbt extends PsbtBase {
+    static fromTransaction<T extends typeof PsbtBase>(this: T, txBuf: Buffer): InstanceType<T>;
+    static fromBuffer<T extends typeof PsbtBase>(this: T, buffer: Buffer): InstanceType<T>;
     private __TX;
     private __TX_BUF_CACHE?;
     private opts;
@@ -18,7 +21,7 @@ export declare class Psbt extends PsbtBase {
         inputResults: boolean[];
     };
     finalizeInput(inputIndex: number): boolean;
-    signInput(inputIndex: number, keyPair: Signer): Psbt;
+    signInput(inputIndex: number, keyPair: Signer): this;
     signInputAsync(inputIndex: number, keyPair: SignerAsync): Promise<void>;
 }
 interface PsbtOptsOptional {