diff --git a/SPEC/FILES.md b/SPEC/FILES.md
index e976a7ea..2857b289 100644
--- a/SPEC/FILES.md
+++ b/SPEC/FILES.md
@@ -30,8 +30,9 @@ If no `content` is passed, then the path is treated as an empty directory
 - cid-version (integer, default 0): the CID version to use when storing the data (storage keys are based on the CID, including it's version)
 - progress (function): a function that will be called with the byte length of chunks as a file is added to ipfs.
 - recursive (boolean): for when a Path is passed, this option can be enabled to add recursively all the files.
-- hashAlg || hash (string): multihash hashing algorithm to use
-- wrapWithDirectory (boolean): adds a wrapping node around the content
+- hashAlg || hash (string): multihash hashing algorithm to use.
+- wrapWithDirectory (boolean): adds a wrapping node around the content.
+- onlyHash (boolean): doesn't actually add the file to IPFS, but rather calculates its hash.
 
 `callback` must follow `function (err, res) {}` signature, where `err` is an error if the operation was not successful. `res` will be an array of:
 
diff --git a/js/src/files.js b/js/src/files.js
index f47ffac1..83256fed 100644
--- a/js/src/files.js
+++ b/js/src/files.js
@@ -19,6 +19,7 @@ const path = require('path')
 const bl = require('bl')
 const isNode = require('detect-node')
 const CID = require('cids')
+const expectTimeout = require('./utils/expect-timeout')
 
 module.exports = (common) => {
   describe('.files', function () {
@@ -334,6 +335,19 @@ module.exports = (common) => {
             expect(file.path).to.equal(smallFile.cid)
           })
       })
+
+      it('files.add with only-hash=true', () => {
+        this.slow(10 * 1000)
+        const content = String(Math.random() + Date.now())
+    
+        return ipfs.files.add(Buffer.from(content), { onlyHash: true })
+          .then(files => {
+            expect(files).to.have.length(1)
+    
+            // 'ipfs.object.get(<hash>)' should timeout because content wasn't actually added
+            return expectTimeout(ipfs.object.get(files[0].hash), 4000)
+          })
+      })
     })
 
     describe('.addReadableStream', () => {
diff --git a/js/src/utils/expect-timeout.js b/js/src/utils/expect-timeout.js
new file mode 100644
index 00000000..51c73307
--- /dev/null
+++ b/js/src/utils/expect-timeout.js
@@ -0,0 +1,16 @@
+'use strict'
+
+/**
+ * Resolve if @param promise hangs for at least @param ms, throw otherwise
+ * @param  {Promise} promise promise that you expect to hang
+ * @param  {Number} ms       millis to wait
+ * @return {Promise}
+ */
+module.exports = (promise, ms) => {
+  return Promise.race([
+    promise.then((out) => {
+      throw new Error('Expected Promise to timeout but it was successful.')
+    }),
+    new Promise((resolve, reject) => setTimeout(resolve, ms))
+  ])
+}