diff --git a/lib/index.js b/lib/index.js
index 657701c3..36cdc7a4 100644
--- a/lib/index.js
+++ b/lib/index.js
@@ -1,12 +1,14 @@
 "use strict";
 
 var Buffer = require("safer-buffer").Buffer;
+var objectAssign = require('object-assign')
 
 var bomHandling = require("./bom-handling"),
     iconv = module.exports;
 
 // All codecs and aliases are kept here, keyed by encoding name/alias.
 // They are lazy loaded in `iconv.getCodec` from `encodings/index.js`.
+// Cannot initialize with Object.create(null) because Boolean(Object.create(null)) === true
 iconv.encodings = null;
 
 // Characters emitted in case of error.
@@ -57,10 +59,13 @@ iconv.toEncoding = iconv.encode;
 iconv.fromEncoding = iconv.decode;
 
 // Search for a codec in iconv.encodings. Cache codec data in iconv._codecDataCache.
-iconv._codecDataCache = {};
+iconv._codecDataCache = Object.create(null);
+
 iconv.getCodec = function getCodec(encoding) {
-    if (!iconv.encodings)
-        iconv.encodings = require("../encodings"); // Lazy load all encoding definitions.
+    if (!iconv.encodings) {
+        var raw = require("../encodings");
+        iconv.encodings = objectAssign(Object.create(null), raw); // Lazy load all encoding definitions.
+    }
     
     // Canonicalize encoding name: strip all non-alphanumeric chars and appended year.
     var enc = iconv._canonicalizeEncoding(encoding);
diff --git a/package.json b/package.json
index b29b1136..47031cfa 100644
--- a/package.json
+++ b/package.json
@@ -43,6 +43,7 @@
         "unorm": "^1.6.0"
     },
     "dependencies": {
+        "object-assign": ">= 4.1.1 < 5.0.0",
         "safer-buffer": ">= 2.1.2 < 3.0.0"
     }
 }
diff --git a/test/main-test.js b/test/main-test.js
index 060bd91d..43b84a1c 100644
--- a/test/main-test.js
+++ b/test/main-test.js
@@ -7,8 +7,26 @@ var testStringLatin1 = "Hello123!£Å÷×çþÿ¿®";
 var testStringBase64 = "SGVsbG8xMjMh";
 var testStringHex = "48656c6c6f31323321";
 
+
+describe("Encoding Existence - Prototype Properties", function() {
+    it("should not detect prototype properties as encodings", function () {
+        assert.equal(iconv.encodingExists("__proto__"), false);
+        assert.equal(iconv.encodingExists("constructor"), false);
+    });
+
+    it("should detect encodings", function () {
+        assert.equal(iconv.encodingExists("utf8"), true);
+    })
+});
+
+describe("Encoding Existence - Codec Data Cache", function () {
+    it("should not detect 'constructor' as encoding when _codecDataCache is defined", function () {
+        assert.equal(iconv.encodingExists("__proto__"), false);
+        assert.equal(iconv.encodingExists("constructor"), false);
+    });
+});
+
 describe("Generic UTF8-UCS2 tests", function() {
-    
     it("Return values are of correct types", function() {
         assert.ok(Buffer.isBuffer(iconv.encode(testString, "utf8")));
         
@@ -45,8 +63,10 @@ describe("Generic UTF8-UCS2 tests", function() {
     });
     
     it("Throws on unknown encodings", function() {
-        assert.throws(function() { iconv.encode("a", "xxx"); });
+        assert. throws(function() { iconv.encode("a", "xxx"); });
         assert.throws(function() { iconv.decode(Buffer.from("a"), "xxx"); });
+        assert.throws(function () { iconv.encode("abc", "constructor") } );
+        assert.throws( function () { iconv.decode(Buffer.from("abc"), "constructor") } );
     });
     
     it("Convert non-strings and non-buffers", function() {
@@ -64,7 +84,7 @@ describe("Generic UTF8-UCS2 tests", function() {
         Object.prototype.permits = function() {};
         Array.prototype.sample2 = function() {};
 
-        iconv._codecDataCache = {}; // Clean up cache so that all encodings are loaded.
+        iconv._codecDataCache = Object.create(null); // Clean up cache so that all encodings are loaded.
 
         assert.strictEqual(iconv.decode(Buffer.from("abc"), "gbk"), "abc");
         assert.strictEqual(iconv.decode(Buffer.from("abc"), "win1251"), "abc");