diff --git a/src/util.js b/src/util.js
index ea3ee8f5..8b6e609f 100644
--- a/src/util.js
+++ b/src/util.js
@@ -64,7 +64,7 @@ export default {
     if (config.zeroCopy && Object.prototype.isPrototypeOf(obj)) {
       const transferables = [];
       this.collectBuffers(obj, transferables);
-      return transferables;
+      return transferables.length ? transferables : undefined;
     }
   },
 
diff --git a/test/general/packet.js b/test/general/packet.js
index da6e31f1..0bc59f14 100644
--- a/test/general/packet.js
+++ b/test/general/packet.js
@@ -1,6 +1,6 @@
 'use strict';
 
-var openpgp = typeof window != 'undefined' && window.openpgp ? window.openpgp : require('../../dist/openpgp');
+var openpgp = typeof window !== 'undefined' && window.openpgp ? window.openpgp : require('../../dist/openpgp');
 
 function stringify(array) {
   if(!Uint8Array.prototype.isPrototypeOf(array)) {
diff --git a/test/general/util.js b/test/general/util.js
index 48e791fd..bad06718 100644
--- a/test/general/util.js
+++ b/test/general/util.js
@@ -144,4 +144,40 @@ describe('Util unit tests', function() {
     });
   });
 
+  describe('getTransferables', function() {
+    var zeroCopyVal,
+      buf1 = new Uint8Array(1),
+      buf2 = new Uint8Array(1),
+      obj = {
+        data1: buf1,
+        data2: buf1,
+        data3: {
+          data4: buf2
+        }
+      };
+
+    beforeEach(function() {
+      zeroCopyVal = openpgp.config.zeroCopy;
+      openpgp.config.zeroCopy = true;
+    });
+
+    afterEach(function() {
+      openpgp.config.zeroCopy = zeroCopyVal;
+    });
+
+    it('should return undefined when zeroCopy is false', function() {
+      openpgp.config.zeroCopy = false;
+      expect(openpgp.util.getTransferables(obj)).to.be.undefined;
+    });
+    it('should return undefined for no input', function() {
+      expect(openpgp.util.getTransferables()).to.be.undefined;
+    });
+    it('should return undefined for an empty oject', function() {
+      expect(openpgp.util.getTransferables({})).to.be.undefined;
+    });
+    it('should return two buffers', function() {
+      expect(openpgp.util.getTransferables(obj)).to.deep.equal([buf1.buffer, buf2.buffer]);
+    });
+  });
+
 });