diff --git a/http.js b/http.js
index 794630f..5434e5b 100644
--- a/http.js
+++ b/http.js
@@ -3,7 +3,7 @@
 
 var ProbeError  = require('./lib/common').ProbeError;
 var needle      = require('needle');
-var merge       = require('deepmerge');
+var lodashMerge       = require('lodash.merge');
 var pkg         = require('./package.json');
 var probeStream = require('./stream');
 var URL         = require('url').URL;
@@ -28,7 +28,8 @@ module.exports = function probeHttp(src, options) {
     var stream, len, finalUrl = src;
 
     try {
-      stream = needle.get(src, merge.all([ defaults, options ]));
+      var needleOptions = lodashMerge({}, defaults, options);
+      stream = needle.get(src, needleOptions);
     } catch (err) {
       reject(err);
       return;
diff --git a/package.json b/package.json
index be2e7e3..46035f2 100644
--- a/package.json
+++ b/package.json
@@ -35,7 +35,7 @@
     "timeout": 5000
   },
   "dependencies": {
-    "deepmerge": "^4.0.0",
+    "lodash.merge": "^4.6.2",
     "needle": "^2.5.2",
     "stream-parser": "~0.3.1"
   },
diff --git a/test/test_http.js b/test/test_http.js
index aaaf7da..1642990 100644
--- a/test/test_http.js
+++ b/test/test_http.js
@@ -232,3 +232,247 @@ describe('probeHttp', function () {
     srv.close();
   });
 });
+
+describe('probeHttpWithAgent', function () {
+  let responder, url, srv;
+
+  let httpAgent = new http.Agent({
+    keepAlive  : true,
+    maxSockets : 1
+  });
+
+  before(function (callback) {
+    srv = http.createServer(function (req, res) {
+      responder(req, res);
+    }).listen(0, 'localhost', function (err) {
+
+      url = URL.format({
+        protocol: 'http',
+        hostname: srv.address().address,
+        port:     srv.address().port,
+        path:     '/'
+      });
+
+      callback(err);
+    });
+  });
+
+  it('should process an image', async function () {
+    responder = function (req, res) {
+      res.writeHead(200);
+      res.write(GIF1x1);
+
+      // response never ends
+    };
+
+    let size = await probe(url, { agent: httpAgent });
+
+    assert.strictEqual(size.width, 1);
+    assert.strictEqual(size.height, 1);
+    assert.strictEqual(size.mime, 'image/gif');
+  });
+
+  it('should return content-length', async function () {
+    responder = function (req, res) {
+      res.writeHead(200, { 'Content-Length': 1234 });
+      res.end(GIF1x1);
+    };
+
+    let size = await probe(url, { agent: httpAgent });
+
+    assert.strictEqual(size.width, 1);
+    assert.strictEqual(size.height, 1);
+    assert.strictEqual(size.length, 1234);
+    assert.strictEqual(size.mime, 'image/gif');
+  });
+
+  // Check that client closes the connection after all parsers fail,
+  //
+  // NOTE: the server output should be large enough so all parsers
+  //       that buffer data will have their first buffer filled
+  //
+  it('should abort request ASAP', async function () {
+    responder = function (req, res) {
+      res.writeHead(200);
+      res.write('this is not an image file,');
+      res.write('it\'s just a bunch of text');
+      // response never ends
+    };
+
+    await assert.rejects(
+      async () => probe(url, { agent: httpAgent }),
+      /unrecognized file format/
+    );
+  });
+
+  it('should fail on 404', async function () {
+    responder = function (req, res) {
+      res.writeHead(404);
+      res.write('not found');
+      // response never ends
+    };
+
+    await assert.rejects(
+      async () => probe(url, { agent: httpAgent }),
+      { statusCode: 404 }
+    );
+  });
+
+  it('should fail on status 201-299 codes', async function () {
+    responder = function (req, res) {
+      res.writeHead(201);
+      res.end(GIF1x1);
+    };
+
+    await assert.rejects(
+      async () => probe(url, { agent: httpAgent }),
+      { statusCode: 201 }
+    );
+  });
+
+  it('should return error if url is not a string', async function () {
+    // for coverage
+    await assert.rejects(
+      async () => probe(123),
+      /URL must be a string/
+    );
+  });
+
+  it('should return error if url is invalid', async function () {
+    await assert.rejects(
+      async () => probe('badurl'),
+      // search error text for both `request` / `got` / Github Actions
+      /(ENOTFOUND badurl)|(Invalid URI)|(getaddrinfo EAI_AGAIN)/
+    );
+  });
+
+  it('should return error if connection fails', async function () {
+    responder = function (req, res) {
+      res.destroy();
+    };
+
+    await assert.rejects(
+      async () => probe(url, { retries: 0 }),
+      { code: 'ECONNRESET' }
+    );
+  });
+
+  it('should add User-Agent to http requests', async function () {
+    let userAgent;
+
+    responder = function (req, res) {
+      userAgent = req.headers['user-agent'];
+
+      res.writeHead(200);
+      res.end(GIF1x1);
+    };
+
+    await probe(url, { agent: httpAgent });
+
+    assert(/^probe/.test(userAgent));
+  });
+
+  it('should allow customize request options', async function () {
+    let userAgent;
+
+    responder = function (req, res) {
+      userAgent = req.headers['user-agent'];
+
+      res.writeHead(200);
+      res.end(GIF1x1);
+    };
+
+    await probe(url, { headers: { 'User-Agent': 'foobar ' } });
+
+    assert(/^foo/.test(userAgent));
+  });
+
+  it('should return url when following redirect', async function () {
+    responder = function (req, res) {
+      if (req.url === '/redirect.gif') {
+        res.writeHead(302, { Location: url + '/empty.gif' });
+        res.end();
+        return;
+      }
+
+      res.writeHead(200);
+      res.end(GIF1x1);
+    };
+
+    let size = await probe(url + '/redirect.gif');
+
+    assert.strictEqual(size.url, url + '/empty.gif');
+    assert.strictEqual(size.width, 1);
+    assert.strictEqual(size.height, 1);
+    assert.strictEqual(size.mime, 'image/gif');
+  });
+
+  it('should follow relative redirect', async function () {
+    responder = function (req, res) {
+      if (req.url === '/path/to/step1.gif') {
+        res.writeHead(302, { Location: '../step2.gif' });
+        res.end();
+        return;
+      }
+
+      if (req.url === '/path/step2.gif') {
+        res.writeHead(302, { Location: 'step3.gif' });
+        res.end();
+        return;
+      }
+
+      res.writeHead(200);
+      res.end(GIF1x1);
+    };
+
+    let size = await probe(url + '/path/to/step1.gif');
+
+    assert.strictEqual(size.url, url + '/path/step3.gif');
+    assert.strictEqual(size.width, 1);
+    assert.strictEqual(size.height, 1);
+    assert.strictEqual(size.mime, 'image/gif');
+  });
+
+  it('should accept gzip-encoded output when not requested by client', async function () {
+    let encoding;
+
+    responder = function (req, res) {
+      encoding = req.headers['accept-encoding'] || 'identity';
+      res.setHeader('content-encoding', 'gzip');
+      res.writeHead(200);
+      res.end(zlib.gzipSync(GIF1x1));
+    };
+
+    let size = await probe(url + '/empty.gif');
+
+    // make sure client requested no compression
+    assert.strictEqual(encoding, 'identity');
+
+    assert.strictEqual(size.width, 1);
+    assert.strictEqual(size.height, 1);
+    assert.strictEqual(size.mime, 'image/gif');
+  });
+
+  it('does not duplicate listeners on .end', async function () {
+    await probe(url + '/path/to/step1.gif', function (err) {
+      if (err) throw err;
+
+      // lets go through all sockets and inspect all socket objects
+      for (let hostTarget in httpAgent.sockets) {
+        // normally, there are 2 internal listeners and 1 needle sets up,
+        // but to be sure the test does not fail even if newer node versions
+        // introduce additional listeners, we use a higher limit.
+        if (hostTarget) {
+          httpAgent.sockets[hostTarget].forEach(function (socket) {
+            socket.listeners('end').length.should.be.below(5, "too many listeners on the socket object's end event");
+          });
+        }
+      }
+    });
+  });
+
+  after(function () {
+    httpAgent.destroy();
+    srv.close();
+  });
+});