diff --git a/src/index.ts b/src/index.ts
index 39a2150..bf7a083 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -252,7 +252,7 @@ const renderCurrentMultisigInfo = (): void => {
             if (lastOrder.type === 'pending' && myAddress) {
                 const myIndex = lastOrder.orderInfo.signers.findIndex(signer => signer.address.equals(myAddress));
                 if (myIndex > -1) {
-                    const mask = 1 << myIndex;
+                    const mask = 1n << BigInt(myIndex);
                     const isSigned = lastOrder.orderInfo.approvalsMask & mask;
 
                     text += isSigned ? ' — You approved' : ` — You haven't approved yet`;
@@ -404,7 +404,7 @@ const renderCurrentOrderInfo = (): void => {
     for (let i = 0; i < signers.length; i++) {
         const signer = signers[i];
         const addressString = makeAddressLink(signer);
-        const mask = 1 << i;
+        const mask = 1n << BigInt(i);
         const isSigned = approvalsMask & mask;
         if (myAddress && isSigned && signer.address.equals(myAddress)) {
             isApprovedByMe = true;
diff --git a/src/multisig/MultisigOrderChecker.ts b/src/multisig/MultisigOrderChecker.ts
index 0c6131f..c0ba9e1 100644
--- a/src/multisig/MultisigOrderChecker.ts
+++ b/src/multisig/MultisigOrderChecker.ts
@@ -20,7 +20,7 @@ export interface MultisigOrderInfo {
     orderId: bigint;
     isExecuted: boolean;
     approvalsNum: number;
-    approvalsMask: number;
+    approvalsMask: bigint;
     threshold: number;
     signers: AddressInfo[];
     expiresAt: Date;
@@ -28,10 +28,13 @@ export interface MultisigOrderInfo {
     stateInitMatches: boolean;
 }
 
-const checkNumber = (n: number) => {
+const checkNumber = (n: number | bigint) => {
     if (n === null) throw new Error('Invalid number');
     if (n === undefined) throw new Error('Invalid number');
-    if (isNaN(n)) throw new Error('Invalid number');
+
+    if (typeof n !== 'bigint') {
+        if (isNaN(n)) throw new Error('Invalid number');
+    }
     if (n < 0) throw new Error('Invalid number');
 }
 
diff --git a/src/multisig/Order.ts b/src/multisig/Order.ts
index 443a8a0..1919c8d 100644
--- a/src/multisig/Order.ts
+++ b/src/multisig/Order.ts
@@ -47,7 +47,7 @@ export function parseOrderData(data: Cell) {
     const threshold = slice.loadUint(8);
     const isExecuted = slice.loadBoolean();
     const signers = cellToArray(slice.loadRef());
-    const approvalsMask = slice.loadUint(1 << 8);
+    const approvalsMask = slice.loadUintBig(1 << 8);
     const approvalsNum = slice.loadUint(8);
     const expirationDate = slice.loadUint(48);
     const order = slice.loadRef();