1 files changed, 1 insertions, 0 deletions
diff --git a/src/0x.ts b/src/0x.ts
index 9613df1be..a395d6dd7 100644
--- a/src/0x.ts
+++ b/src/0x.ts
@@ -163,6 +163,7 @@ export class ZeroEx {
      * @return  An instance of the 0x.js ZeroEx class.
      */
     constructor(provider: Web3Provider, config?: ZeroExConfig) {
+        assert.isWeb3Provider('provider', provider);
         if (_.isUndefined((provider as any).sendAsync)) {
             // Web3@1.0 provider doesn't support synchronous http requests,
             // so it only has `send` method, instead of `send and `sendAsync` in web3@0.x.x