diff --git a/lib/core/dispatchRequest.js b/lib/core/dispatchRequest.js
index c8267ad..18d4635 100644
--- a/lib/core/dispatchRequest.js
+++ b/lib/core/dispatchRequest.js
@@ -47,6 +47,13 @@ module.exports = function dispatchRequest(config) {
     }
   );
 
+  // Remove header where value is null
+  utils.forEach(config.headers, function deleteNullValueHeaders(value, key) {
+    if (value === null) {
+      delete config.headers[key];
+    }
+  });
+
   var adapter = config.adapter || defaults.adapter;
 
   return adapter(config).then(function onAdapterResolution(response) {
diff --git a/lib/utils.js b/lib/utils.js
index e028c67..27938d3 100644
--- a/lib/utils.js
+++ b/lib/utils.js
@@ -294,6 +294,11 @@ function deepMerge(/* obj1, obj2, obj3, ... */) {
     }
   }
 
+  var lastArgument = arguments[arguments.length - 1];
+  if (lastArgument === null || typeof lastArgument === 'undefined') {
+    return lastArgument;
+  }
+
   for (var i = 0, l = arguments.length; i < l; i++) {
     forEach(arguments[i], assignValue);
   }
diff --git a/test/specs/headers.spec.js b/test/specs/headers.spec.js
index 5a8b1a8..e7fe4fa 100644
--- a/test/specs/headers.spec.js
+++ b/test/specs/headers.spec.js
@@ -42,6 +42,21 @@ describe('headers', function () {
     });
   });
 
+  it('should not set header if value is null', function (done) {
+    expect(axios.defaults.headers.common['Accept']).toEqual('application/json, text/plain, */*');
+
+    axios('/foo', {
+      headers: {
+        Accept: null
+      }
+    });
+
+    getAjaxRequest().then(function (request) {
+      expect(typeof request.requestHeaders['Accept']).toEqual('undefined');
+      done();
+    });
+  });
+
   it('should add extra headers for post', function (done) {
     var headers = axios.defaults.headers.common;
 
diff --git a/test/specs/utils/deepMerge.spec.js b/test/specs/utils/deepMerge.spec.js
index d879593..75265d9 100644
--- a/test/specs/utils/deepMerge.spec.js
+++ b/test/specs/utils/deepMerge.spec.js
@@ -26,7 +26,7 @@ describe('utils::deepMerge', function () {
 
   it('should deepMerge recursively', function () {
     var a = {foo: {bar: 123}};
-    var b = {foo: {baz: 456}, bar: {qux: 789}};
+    var b = {foo: {baz: 456}, bar: {qux: null}};
 
     expect(deepMerge(a, b)).toEqual({
       foo: {
@@ -34,7 +34,7 @@ describe('utils::deepMerge', function () {
         baz: 456
       },
       bar: {
-        qux: 789
+        qux: null
       }
     });
   });
@@ -54,13 +54,13 @@ describe('utils::deepMerge', function () {
   });
 
   it('handles null and undefined arguments', function () {
-    expect(deepMerge(undefined, undefined)).toEqual({});
+    expect(deepMerge(undefined, undefined)).toEqual(undefined);
     expect(deepMerge(undefined, {foo: 123})).toEqual({foo: 123});
-    expect(deepMerge({foo: 123}, undefined)).toEqual({foo: 123});
+    expect(deepMerge({foo: 123}, undefined)).toEqual(undefined);
 
-    expect(deepMerge(null, null)).toEqual({});
+    expect(deepMerge(null, null)).toEqual(null);
     expect(deepMerge(null, {foo: 123})).toEqual({foo: 123});
-    expect(deepMerge({foo: 123}, null)).toEqual({foo: 123});
+    expect(deepMerge({foo: 123}, null)).toEqual(null);
   });
 });