diff --git a/src/json-rpc-provider-types.test-d.ts b/src/json-rpc-provider-types.test-d.ts
index 3891c8142..f616d72bb 100644
--- a/src/json-rpc-provider-types.test-d.ts
+++ b/src/json-rpc-provider-types.test-d.ts
@@ -1,12 +1,34 @@
-import { expectAssignable, expectNotAssignable } from 'tsd';
-import EthQuery from '@metamask/eth-query';
 import { Web3Provider } from '@ethersproject/providers';
+import EthQuery from '@metamask/eth-query';
+import { expectAssignable, expectNotAssignable } from 'tsd';
 
-import type {
-  LegacyEthereumProvider
-} from '.';
+import type { JsonRpcRequest, LegacyEthereumProvider } from '.';
 
 // Known legacy providers
-
 expectAssignable<LegacyEthereumProvider>(new EthQuery({} as any));
 expectAssignable<LegacyEthereumProvider>(new Web3Provider({} as any));
+expectAssignable<LegacyEthereumProvider>({
+  send: async (method: string, params: string[]) =>
+    Promise.resolve([method, params]),
+});
+expectAssignable<LegacyEthereumProvider>({
+  // eslint-disable-next-line @typescript-eslint/no-empty-function
+  send: (_req: JsonRpcRequest, _cb: () => void) => {},
+});
+expectAssignable<LegacyEthereumProvider>({
+  send: async (req: JsonRpcRequest, _cb: (_x: null, _result: null) => void) =>
+    Promise.resolve(req),
+});
+
+expectNotAssignable<LegacyEthereumProvider>({ foo: '123' });
+expectNotAssignable<LegacyEthereumProvider>({ send: '123' });
+
+expectNotAssignable<LegacyEthereumProvider>({
+  send: (method: string, params: string[]) => [method, params],
+});
+expectNotAssignable<LegacyEthereumProvider>({
+  send: async (
+    req: JsonRpcRequest,
+    _cb: (_x: null, _result: undefined) => void,
+  ) => Promise.resolve(req),
+});
diff --git a/src/json-rpc-provider-types.ts b/src/json-rpc-provider-types.ts
index a6bd68e70..1f9d97b28 100644
--- a/src/json-rpc-provider-types.ts
+++ b/src/json-rpc-provider-types.ts
@@ -33,20 +33,27 @@ export type EIP1993Provider = SafeEventEmitter & {
  * [EIP-1193](https://eips.ethereum.org/EIPS/eip-1193). It is not compliant with
  * any Ethereum provider standard.
  */
-export type LegacyEthereumProvider = LegacyEthersProvider | LegacyEthJsQueryProvider | LegacyWeb3Provider;
+export type LegacyEthereumProvider =
+  | LegacyEthersProvider
+  | LegacyEthJsQueryProvider
+  | LegacyWeb3Provider;
 
-type LegacyWeb3Provider = {
+type LegacyEthersProvider = {
   /**
-   * Send a provider request asynchronously.
+   * Send a provider request asynchronously. (ethers v5 Web3Provider)
    *
-   * @param req - The request to send.
-   * @param callback - A function that is called upon the success or failure of the request.
+   * @param method - The RPC method to call.
+   * @param params - Array with method parameters.
+   * @returns A promise resolving with the result of the RPC call, or rejecting on failure.
    */
-  send?<Result extends Json = Json>(
-    req: Partial<JsonRpcRequest>,
-    callback: SendAsyncCallback<Result>,
-  ): void;
-}
+  send(method: string, params: any[]): Promise<Json>;
+  /*
+  send<Result extends Json = Json>(
+    method: string,
+    params: any[],
+  ): Promise<Result>;
+  */
+};
 
 type LegacyEthJsQueryProvider = {
   /**
@@ -55,24 +62,20 @@ type LegacyEthJsQueryProvider = {
    * @param req - The request to send.
    * @param callback - A function that is called upon the success or failure of the request.
    */
-  sendAsync?<Result extends Json = Json>(
+  sendAsync<Result extends Json = Json>(
     req: Partial<JsonRpcRequest>,
     callback: SendAsyncCallback<Result>,
   ): void;
 };
 
-type LegacyEthersProvider = {
+type LegacyWeb3Provider = {
   /**
-   * Send a provider request asynchronously. (ethers v5 Web3Provider)
+   * Send a provider request asynchronously.
    *
-   * @param method - The RPC method to call.
-   * @param params - Array with method parameters.
-   * @returns - A promise resolving with the result of the RPC call, or rejecting on failure.
+   * @param req - The request to send.
+   * @param callback - A function that is called upon the success or failure of the request.
    */
-  send?<Result extends Json = Json>(
-    method: string,
-    params: any[],
-  ): Promise<Result>;
+  send(req: Partial<JsonRpcRequest>, callback: SendAsyncCallback<Json>): void;
 };
 
 type SendAsyncCallback<Result extends Json> = (