diff --git a/lib/dns.js b/lib/dns.js
index e77542457b5cd1..e165b1bc0d2f05 100644
--- a/lib/dns.js
+++ b/lib/dns.js
@@ -243,7 +243,7 @@ function resolver(bindingName) {
 }
 
 
-var resolveMap = {};
+var resolveMap = Object.create(null);
 exports.resolve4 = resolveMap.A = resolver('queryA');
 exports.resolve6 = resolveMap.AAAA = resolver('queryAaaa');
 exports.resolveCname = resolveMap.CNAME = resolver('queryCname');
diff --git a/test/parallel/test-c-ares.js b/test/parallel/test-c-ares.js
index 8c2178ead6a93d..66ae0e0a4adf33 100644
--- a/test/parallel/test-c-ares.js
+++ b/test/parallel/test-c-ares.js
@@ -27,6 +27,11 @@ assert.throws(function() {
   dns.resolve('www.google.com', 'HI');
 }, /Unknown type/);
 
+// Try calling resolve with an unsupported type that's an object key
+assert.throws(function() {
+  dns.resolve('www.google.com', 'toString');
+}, /Unknown type/);
+
 // Windows doesn't usually have an entry for localhost 127.0.0.1 in
 // C:\Windows\System32\drivers\etc\hosts
 // so we disable this test on Windows.