diff --git a/packages/babel-helpers/src/helpers.js b/packages/babel-helpers/src/helpers.js
index b25b747c97..b521cb06b9 100644
--- a/packages/babel-helpers/src/helpers.js
+++ b/packages/babel-helpers/src/helpers.js
@@ -587,7 +587,7 @@ helpers.wrapNativeSuper = helper("7.0.0-beta.0")`
 helpers.instanceof = helper("7.0.0-beta.0")`
   export default function _instanceof(left, right) {
     if (right != null && typeof Symbol !== "undefined" && right[Symbol.hasInstance]) {
-      return right[Symbol.hasInstance](left);
+      return !!right[Symbol.hasInstance](left);
     } else {
       return left instanceof right;
     }
diff --git a/packages/babel-plugin-transform-instanceof/test/fixtures/instanceof/instanceof/exec.js b/packages/babel-plugin-transform-instanceof/test/fixtures/instanceof/instanceof/exec.js
index 187f18b8f7..eb681c286f 100644
--- a/packages/babel-plugin-transform-instanceof/test/fixtures/instanceof/instanceof/exec.js
+++ b/packages/babel-plugin-transform-instanceof/test/fixtures/instanceof/instanceof/exec.js
@@ -4,6 +4,11 @@ foo[Symbol.hasInstance]= function () { return true; };
 var bar = {};
 
 expect(bar instanceof foo).toBe(true);
+
+var qux = {};
+qux[Symbol.hasInstance]= function () { return NaN };
+expect(bar instanceof qux).toBe(false);
+
 expect(new String).toBeInstanceOf(String);
 
 //