diff --git a/lib/transaction.js b/lib/transaction.js
index 1d91feb8b2..99ba167bf2 100644
--- a/lib/transaction.js
+++ b/lib/transaction.js
@@ -121,48 +121,46 @@ exports.SignedTransaction = SignedTransaction;
 class Action extends Enum {
 }
 exports.Action = Action;
-const SCHEMA = {
-    Signature: { kind: 'struct', fields: [['keyType', 'u8'], ['data', [32]]] },
-    SignedTransaction: { kind: 'struct', fields: [['transaction', Transaction], ['signature', Signature]] },
-    Transaction: {
-        kind: 'struct', fields: [['signerId', 'string'], ['publicKey', PublicKey], ['nonce', 'u64'], ['receiverId', 'string'], ['actions', [Action]]]
-    },
-    PublicKey: {
-        kind: 'struct', fields: [['keyType', 'u8'], ['data', [32]]]
-    },
-    AccessKey: { kind: 'struct', fields: [
-            ['nonce', 'u64'],
-            ['permission', AccessKeyPermission],
-        ] },
-    AccessKeyPermission: { kind: 'enum', field: 'enum', values: [
-            ['functionCall', FunctionCallPermission],
-            ['fullAccess', FullAccessPermission],
-        ] },
-    FunctionCallPermission: { kind: 'struct', fields: [
-            ['allowance', { kind: 'option', type: 'u128' }],
-            ['receiverId', 'string'],
-            ['methodNames', ['string']],
-        ] },
-    FullAccessPermission: { kind: 'struct', fields: [] },
-    Action: { kind: 'enum', field: 'enum', values: [
-            ['createAccount', CreateAccount],
-            ['deployContract', DeployContract],
-            ['functionCall', functionCall],
-            ['transfer', transfer],
-            ['stake', stake],
-            ['addKey', addKey],
-            ['deleteKey', deleteKey],
-            ['deleteAccount', deleteAccount],
-        ] },
-    CreateAccount: { kind: 'struct', fields: [] },
-    DeployContract: { kind: 'struct', fields: [['code', ['u8']]] },
-    FunctionCall: { kind: 'struct', fields: [['methodName', 'string'], ['args', ['u8']], ['gas', 'u64'], ['deposit', 'u128']] },
-    Transfer: { kind: 'struct', fields: [['deposit', 'u128']] },
-    Stake: { kind: 'struct', fields: [['stake', 'u128'], ['publicKey', PublicKey]] },
-    AddKey: { kind: 'struct', fields: [['publicKey', PublicKey], ['accessKey', AccessKey]] },
-    DeleteKey: { kind: 'struct', fields: [['publicKey', PublicKey]] },
-    DeleteAccount: { kind: 'struct', fields: [['beneficiaryId', 'string']] },
-};
+const SCHEMA = new Map([
+    [Signature, { kind: 'struct', fields: [['keyType', 'u8'], ['data', [32]]] }],
+    [SignedTransaction, { kind: 'struct', fields: [['transaction', Transaction], ['signature', Signature]] }],
+    [Transaction, { kind: 'struct', fields: [['signerId', 'string'], ['publicKey', PublicKey], ['nonce', 'u64'], ['receiverId', 'string'], ['actions', [Action]]] }],
+    [PublicKey, {
+            kind: 'struct', fields: [['keyType', 'u8'], ['data', [32]]]
+        }],
+    [AccessKey, { kind: 'struct', fields: [
+                ['nonce', 'u64'],
+                ['permission', AccessKeyPermission],
+            ] }],
+    [AccessKeyPermission, { kind: 'enum', field: 'enum', values: [
+                ['functionCall', FunctionCallPermission],
+                ['fullAccess', FullAccessPermission],
+            ] }],
+    [FunctionCallPermission, { kind: 'struct', fields: [
+                ['allowance', { kind: 'option', type: 'u128' }],
+                ['receiverId', 'string'],
+                ['methodNames', ['string']],
+            ] }],
+    [FullAccessPermission, { kind: 'struct', fields: [] }],
+    [Action, { kind: 'enum', field: 'enum', values: [
+                ['createAccount', CreateAccount],
+                ['deployContract', DeployContract],
+                ['functionCall', functionCall],
+                ['transfer', transfer],
+                ['stake', stake],
+                ['addKey', addKey],
+                ['deleteKey', deleteKey],
+                ['deleteAccount', deleteAccount],
+            ] }],
+    [CreateAccount, { kind: 'struct', fields: [] }],
+    [DeployContract, { kind: 'struct', fields: [['code', ['u8']]] }],
+    [FunctionCall, { kind: 'struct', fields: [['methodName', 'string'], ['args', ['u8']], ['gas', 'u64'], ['deposit', 'u128']] }],
+    [Transfer, { kind: 'struct', fields: [['deposit', 'u128']] }],
+    [Stake, { kind: 'struct', fields: [['stake', 'u128'], ['publicKey', PublicKey]] }],
+    [AddKey, { kind: 'struct', fields: [['publicKey', PublicKey], ['accessKey', AccessKey]] }],
+    [DeleteKey, { kind: 'struct', fields: [['publicKey', PublicKey]] }],
+    [DeleteAccount, { kind: 'struct', fields: [['beneficiaryId', 'string']] }],
+]);
 async function signTransaction(receiverId, nonce, actions, signer, accountId, networkId) {
     const publicKey = new PublicKey(await signer.getPublicKey(accountId, networkId));
     const transaction = new Transaction({ signerId: accountId, publicKey, nonce, receiverId, actions });
diff --git a/lib/utils/serialize.d.ts b/lib/utils/serialize.d.ts
index b2100acecc..c0fa4fc110 100644
--- a/lib/utils/serialize.d.ts
+++ b/lib/utils/serialize.d.ts
@@ -2,6 +2,7 @@
 import BN from 'bn.js';
 export declare function base_encode(value: Uint8Array | string): string;
 export declare function base_decode(value: string): Uint8Array;
+export declare type Schema = Map<Function, any>;
 export declare class BinaryWriter {
     buf: Buffer;
     length: number;
@@ -30,5 +31,5 @@ export declare class BinaryReader {
     read_fixed_array(len: number): Uint8Array;
     read_array(fn: any): any[];
 }
-export declare function serialize(schema: any, obj: any): Uint8Array;
-export declare function deserialize(schema: any, classType: any, buffer: Buffer): any;
+export declare function serialize(schema: Schema, obj: any): Uint8Array;
+export declare function deserialize(schema: Schema, classType: any, buffer: Buffer): any;
diff --git a/lib/utils/serialize.js b/lib/utils/serialize.js
index 5dd1c3f759..a4beea05f3 100644
--- a/lib/utils/serialize.js
+++ b/lib/utils/serialize.js
@@ -150,19 +150,20 @@ function serializeField(schema, value, fieldType, writer) {
     }
 }
 function serializeStruct(schema, obj, writer) {
-    const className = obj.constructor.name;
-    if (schema[className] === undefined) {
-        throw new Error(`Class ${className} is missing in schema`);
+    console.log('serializeStruct', schema);
+    const structSchema = schema.get(obj.constructor);
+    if (!structSchema) {
+        throw new Error(`Class ${obj.constructor.name} is missing in schema`);
     }
-    if (schema[className].kind === 'struct') {
-        schema[className].fields.map(([fieldName, fieldType]) => {
+    if (structSchema.kind === 'struct') {
+        structSchema.fields.map(([fieldName, fieldType]) => {
             serializeField(schema, obj[fieldName], fieldType, writer);
         });
     }
-    else if (schema[className].kind === 'enum') {
-        const name = obj[schema[className].field];
-        for (let idx = 0; idx < schema[className].values.length; ++idx) {
-            const [fieldName, fieldType] = schema[className].values[idx];
+    else if (structSchema.kind === 'enum') {
+        const name = obj[structSchema.field];
+        for (let idx = 0; idx < structSchema.values.length; ++idx) {
+            const [fieldName, fieldType] = structSchema.values[idx];
             if (fieldName === name) {
                 writer.write_u8(idx);
                 serializeField(schema, obj[fieldName], fieldType, writer);
@@ -171,7 +172,7 @@ function serializeStruct(schema, obj, writer) {
         }
     }
     else {
-        throw new Error(`Unexpected schema kind: ${schema[className].kind} for ${className}`);
+        throw new Error(`Unexpected schema kind: ${structSchema.kind} for ${obj.constructor.name}`);
     }
 }
 /// Serialize given object using schema of the form:
@@ -199,7 +200,7 @@ function deserializeField(schema, fieldType, reader) {
     }
 }
 function deserializeStruct(schema, classType, reader) {
-    const fields = schema[classType.name].fields.map(([fieldName, fieldType]) => {
+    const fields = schema.get(classType).fields.map(([fieldName, fieldType]) => {
         return deserializeField(schema, fieldType, reader);
     });
     return new classType(...fields);
diff --git a/src.ts/transaction.ts b/src.ts/transaction.ts
index e805353ade..0b79cdc845 100644
--- a/src.ts/transaction.ts
+++ b/src.ts/transaction.ts
@@ -149,28 +149,27 @@ export class Action extends Enum {
     deleteAccount: DeleteAccount;
 }
 
-const SCHEMA = {
-    Signature: {kind: 'struct', fields: [['keyType', 'u8'], ['data', [32]]]},
-    SignedTransaction: {kind: 'struct', fields: [['transaction', Transaction], ['signature', Signature]]},
-    Transaction: {
-        kind: 'struct', fields: [['signerId', 'string'], ['publicKey', PublicKey], ['nonce', 'u64'], ['receiverId', 'string'], ['actions', [Action]]] },
-    PublicKey: {
-            kind: 'struct', fields: [['keyType', 'u8'], ['data', [32]]] },
-    AccessKey: { kind: 'struct', fields: [
+const SCHEMA = new Map<Function, any>([
+    [Signature, {kind: 'struct', fields: [['keyType', 'u8'], ['data', [32]]]}],
+    [SignedTransaction, {kind: 'struct', fields: [['transaction', Transaction], ['signature', Signature]]}],
+    [Transaction, { kind: 'struct', fields: [['signerId', 'string'], ['publicKey', PublicKey], ['nonce', 'u64'], ['receiverId', 'string'], ['actions', [Action]]] }],
+    [PublicKey, {
+            kind: 'struct', fields: [['keyType', 'u8'], ['data', [32]]] }],
+    [AccessKey, { kind: 'struct', fields: [
         ['nonce', 'u64'],
         ['permission', AccessKeyPermission],
-    ]},
-    AccessKeyPermission: {kind: 'enum', field: 'enum', values: [
+    ]}],
+    [AccessKeyPermission, {kind: 'enum', field: 'enum', values: [
         ['functionCall', FunctionCallPermission],
         ['fullAccess', FullAccessPermission],
-    ]},
-    FunctionCallPermission: {kind: 'struct', fields: [
+    ]}],
+    [FunctionCallPermission, {kind: 'struct', fields: [
         ['allowance', {kind: 'option', type: 'u128'}],
         ['receiverId', 'string'],
         ['methodNames', ['string']],
-    ]},
-    FullAccessPermission: {kind: 'struct', fields: []},
-    Action: {kind: 'enum', field: 'enum', values: [
+    ]}],
+    [FullAccessPermission, {kind: 'struct', fields: []}],
+    [Action, {kind: 'enum', field: 'enum', values: [
         ['createAccount', CreateAccount],
         ['deployContract', DeployContract],
         ['functionCall', functionCall],
@@ -179,16 +178,16 @@ const SCHEMA = {
         ['addKey', addKey],
         ['deleteKey', deleteKey],
         ['deleteAccount', deleteAccount],
-    ]},
-    CreateAccount: { kind: 'struct', fields: [] },
-    DeployContract: { kind: 'struct', fields: [['code', ['u8']]] },
-    FunctionCall: { kind: 'struct', fields: [['methodName', 'string'], ['args', ['u8']], ['gas', 'u64'], ['deposit', 'u128']] },
-    Transfer: { kind: 'struct', fields: [['deposit', 'u128']] },
-    Stake: { kind: 'struct', fields: [['stake', 'u128'], ['publicKey', PublicKey]] },
-    AddKey: { kind: 'struct', fields: [['publicKey', PublicKey], ['accessKey', AccessKey]] },
-    DeleteKey: { kind: 'struct', fields: [['publicKey', PublicKey]] },
-    DeleteAccount: { kind: 'struct', fields: [['beneficiaryId', 'string']] },
-};
+    ]}],
+    [CreateAccount, { kind: 'struct', fields: [] }],
+    [DeployContract, { kind: 'struct', fields: [['code', ['u8']]] }],
+    [FunctionCall, { kind: 'struct', fields: [['methodName', 'string'], ['args', ['u8']], ['gas', 'u64'], ['deposit', 'u128']] }],
+    [Transfer, { kind: 'struct', fields: [['deposit', 'u128']] }],
+    [Stake, { kind: 'struct', fields: [['stake', 'u128'], ['publicKey', PublicKey]] }],
+    [AddKey, { kind: 'struct', fields: [['publicKey', PublicKey], ['accessKey', AccessKey]] }],
+    [DeleteKey, { kind: 'struct', fields: [['publicKey', PublicKey]] }],
+    [DeleteAccount, { kind: 'struct', fields: [['beneficiaryId', 'string']] }],
+]);
 
 export async function signTransaction(receiverId: string, nonce: number, actions: Action[], signer: Signer, accountId?: string, networkId?: string): Promise<[Uint8Array, SignedTransaction]> {
     const publicKey = new PublicKey(await signer.getPublicKey(accountId, networkId));
diff --git a/src.ts/utils/serialize.ts b/src.ts/utils/serialize.ts
index b41570a1a8..0e0cb2612f 100644
--- a/src.ts/utils/serialize.ts
+++ b/src.ts/utils/serialize.ts
@@ -16,6 +16,8 @@ export function base_decode(value: string): Uint8Array {
 
 const INITIAL_LENGTH = 1024;
 
+export type Schema = Map<Function, any>;
+
 /// Binary encoder.
 export class BinaryWriter {
     buf: Buffer;
@@ -141,7 +143,7 @@ export class BinaryReader {
     }
 }
 
-function serializeField(schema: any, value: any, fieldType: any, writer: any) {
+function serializeField(schema: Schema, value: any, fieldType: any, writer: any) {
     if (typeof fieldType === 'string') {
         writer[`write_${fieldType}`](value);
     } else if (fieldType instanceof Array) {
@@ -168,19 +170,20 @@ function serializeField(schema: any, value: any, fieldType: any, writer: any) {
     }
 }
 
-function serializeStruct(schema: any, obj: any, writer: any) {
-    const className = obj.constructor.name;
-    if (schema[className] === undefined) {
-        throw new Error(`Class ${className} is missing in schema`);
+function serializeStruct(schema: Schema, obj: any, writer: any) {
+    console.log('serializeStruct', schema);
+    const structSchema = schema.get(obj.constructor);
+    if (!structSchema) {
+        throw new Error(`Class ${obj.constructor.name} is missing in schema`);
     }
-    if (schema[className].kind === 'struct') {
-        schema[className].fields.map(([fieldName, fieldType]: [any, any]) => {
+    if (structSchema.kind === 'struct') {
+        structSchema.fields.map(([fieldName, fieldType]: [any, any]) => {
             serializeField(schema, obj[fieldName], fieldType, writer);
         });
-    } else if (schema[className].kind === 'enum') {
-        const name = obj[schema[className].field];
-        for (let idx = 0; idx < schema[className].values.length; ++idx) {
-            const [fieldName, fieldType]: [any, any] = schema[className].values[idx];
+    } else if (structSchema.kind === 'enum') {
+        const name = obj[structSchema.field];
+        for (let idx = 0; idx < structSchema.values.length; ++idx) {
+            const [fieldName, fieldType]: [any, any] = structSchema.values[idx];
             if (fieldName === name) {
                 writer.write_u8(idx);
                 serializeField(schema, obj[fieldName], fieldType, writer);
@@ -188,19 +191,19 @@ function serializeStruct(schema: any, obj: any, writer: any) {
             }
         }
     } else {
-        throw new Error(`Unexpected schema kind: ${schema[className].kind} for ${className}`);
+        throw new Error(`Unexpected schema kind: ${structSchema.kind} for ${obj.constructor.name}`);
     }
 }
 
 /// Serialize given object using schema of the form:
 /// { class_name -> [ [field_name, field_type], .. ], .. }
-export function serialize(schema: any, obj: any): Uint8Array {
+export function serialize(schema: Schema, obj: any): Uint8Array {
     const writer = new BinaryWriter();
     serializeStruct(schema, obj, writer);
     return writer.toArray();
 }
 
-function deserializeField(schema: any, fieldType: any, reader: any): any {
+function deserializeField(schema: Schema, fieldType: any, reader: any): any {
     if (typeof fieldType === 'string') {
         return reader[`read_${fieldType}`]();
     } else if (fieldType instanceof Array) {
@@ -214,15 +217,15 @@ function deserializeField(schema: any, fieldType: any, reader: any): any {
     }
 }
 
-function deserializeStruct(schema: any, classType: any, reader: any) {
-    const fields = schema[classType.name].fields.map(([fieldName, fieldType]: [any, any]) => {
+function deserializeStruct(schema: Schema, classType: any, reader: any) {
+    const fields = schema.get(classType).fields.map(([fieldName, fieldType]: [any, any]) => {
         return deserializeField(schema, fieldType, reader);
     });
     return new classType(...fields);
 }
 
 /// Deserializes object from bytes using schema.
-export function deserialize(schema: any, classType: any, buffer: Buffer): any {
+export function deserialize(schema: Schema, classType: any, buffer: Buffer): any {
     const reader = new BinaryReader(buffer);
     return deserializeStruct(schema, classType, reader);
 }
diff --git a/test/serialize.test.js b/test/serialize.test.js
index 275b9d8679..eb3749f853 100644
--- a/test/serialize.test.js
+++ b/test/serialize.test.js
@@ -12,7 +12,7 @@ class Test {
 
 test('serialize object', async () => {
     const value = new Test(255, 20, '123', [1, 2, 3]);
-    const schema = { 'Test': {kind: 'struct', fields: [['x', 'u8'], ['y', 'u64'], ['z', 'string'], ['q', [3]]] } };
+    const schema = new Map([[Test, {kind: 'struct', fields: [['x', 'u8'], ['y', 'u64'], ['z', 'string'], ['q', [3]]] }]]);
     let buf = nearlib.utils.serialize.serialize(schema, value);
     let new_value = nearlib.utils.serialize.deserialize(schema, Test, buf);
     expect(new_value.x).toEqual(255);