diff --git a/src/Client/License.php b/src/Client/License.php
index 9a0d387..a9cc041 100644
--- a/src/Client/License.php
+++ b/src/Client/License.php
@@ -104,6 +104,9 @@ public function getContentInfo(LicenseRequest $request, string $access_token, Ht
         $end_point = $this->_config->getEndPoints()['license_info'];
         $request_url = $end_point . '?' . http_build_query($request);
         $headers = APIUtils::generateCommonAPIHeaders($this->_config, $access_token);
+        if (!empty($request->getRequestId())) {
+            $headers['headers']['x-request-id'] = $request->getRequestId();
+        }
         $raw_response = $http_client->doGet($request_url, $headers);
         $license_response = new LicenseResponse(json_decode($raw_response, true));
         return $license_response;
@@ -127,7 +130,10 @@ public function getContentLicense(LicenseRequest $request, string $access_token,
         $end_point = $this->_config->getEndPoints()['license'];
         $request_url = $end_point . '?' . http_build_query($request);
         $headers = APIUtils::generateCommonAPIHeaders($this->_config, $access_token);
-        
+        if (!empty($request->getRequestId())) {
+            $headers['headers']['x-request-id'] = $request->getRequestId();
+        }
+
         if ($request->getLicenseReference() != null) {
             $raw_response = $http_client->doPost($request_url, $headers, $request->getLicenseReference());
         } else {
@@ -157,6 +163,9 @@ public function getMemberProfile(LicenseRequest $request, string $access_token,
         $end_point = $this->_config->getEndPoints()['user_profile'];
         $request_url = $end_point . '?' . http_build_query($request);
         $headers = APIUtils::generateCommonAPIHeaders($this->_config, $access_token);
+        if (!empty($request->getRequestId())) {
+            $headers['headers']['x-request-id'] = $request->getRequestId();
+        }
         $raw_response = $http_client->doGet($request_url, $headers);
         $license_response = new LicenseResponse(json_decode($raw_response, true));
         return $license_response;
@@ -177,6 +186,9 @@ public function abandonLicense(LicenseRequest $request, string $access_token, Ht
         $end_point = $this->_config->getEndPoints()['abandon'];
         $request_url = $end_point . '?' . http_build_query($request);
         $headers = APIUtils::generateCommonAPIHeaders($this->_config, $access_token);
+        if (!empty($request->getRequestId())) {
+            $headers['headers']['x-request-id'] = $request->getRequestId();
+        }
         $response = $http_client->doGet($request_url, $headers);
         $code = (int) $response->getContents();
         
@@ -241,6 +253,9 @@ public function downloadAssetRequest(LicenseRequest $request, string $access_tok
         
         $url = $purchase_details->getUrl();
         $headers = APIUtils::generateCommonAPIHeaders($this->_config, $access_token);
+        if (!empty($request->getRequestId())) {
+            $headers['headers']['x-request-id'] = $request->getRequestId();
+        }
         $headers['allow_redirects'] = false;
         $client_handler = $http_client->getHandlerStack();
         //adds middleware in the client which controls the redirection behaviour.
diff --git a/src/Client/LicenseHistory.php b/src/Client/LicenseHistory.php
index 5bb1cdf..fa531d0 100644
--- a/src/Client/LicenseHistory.php
+++ b/src/Client/LicenseHistory.php
@@ -140,6 +140,9 @@ private function _doOnError()
     private function _getFiles(LicenseHistoryRequest $license_file_request, string $access_token = null) : LicenseHistoryResponse
     {
         $headers = APIUtils::generateCommonAPIHeaders($this->_config, $access_token);
+        if (!empty($license_file_request->getRequestId())) {
+            $headers['headers']['x-request-id'] = $license_file_request->getRequestId();
+        }
         $end_point = $this->_config->getEndPoints()['license_history'];
         $request_url = $end_point . '?' . http_build_query($license_file_request);
         $offset_value = $this->_offset;
diff --git a/src/Client/SearchCategory.php b/src/Client/SearchCategory.php
index 9f70557..e08afcb 100644
--- a/src/Client/SearchCategory.php
+++ b/src/Client/SearchCategory.php
@@ -52,6 +52,9 @@ public function getCategory(SearchCategoryRequest $request, string $access_token
         $end_point = $this->_config->getEndPoints()['category'];
         $request_url = $end_point . '?' . http_build_query($request);
         $headers = APIUtils::generateCommonAPIHeaders($this->_config, $access_token);
+        if (!empty($request->getRequestId())) {
+            $headers['headers']['x-request-id'] = $request->getRequestId();
+        }
         $raw_response = $http_client->doGet($request_url, $headers);
         $search_category_response = new SearchCategoryResponse(json_decode($raw_response, true));
         return $search_category_response;
@@ -75,6 +78,9 @@ public function getCategoryTree(SearchCategoryRequest $request, string $access_t
         $end_point = $this->_config->getEndPoints()['category_tree'];
         $request_url = $end_point . '?' . http_build_query($request);
         $headers = APIUtils::generateCommonAPIHeaders($this->_config, $access_token);
+        if (!empty($request->getRequestId())) {
+            $headers['headers']['x-request-id'] = $request->getRequestId();
+        }
         $raw_response = $http_client->doGet($request_url, $headers);
         return $this->_createSearchCategoryResponseArray(json_decode($raw_response, true));
     }
diff --git a/src/Client/SearchFiles.php b/src/Client/SearchFiles.php
index 8f50cdf..7d5d022 100644
--- a/src/Client/SearchFiles.php
+++ b/src/Client/SearchFiles.php
@@ -82,7 +82,7 @@ class SearchFiles
     
     /**
      * Custom http client object
-     * @var HttpInterface
+     * @var HttpClientInterface
      */
     private $_http_client;
     
@@ -134,6 +134,9 @@ public function getFiles(SearchFilesRequest $search_file_request, string $access
     {
         $this->_http_method = $this->_getHttpMethod($search_file_request);
         $headers = APIUtils::generateCommonAPIHeaders($this->_config, $access_token);
+        if (!empty($search_file_request->getRequestId())) {
+            $headers['headers']['x-request-id'] = $search_file_request->getRequestId();
+        }
         $end_point = $this->_config->getEndPoints()['search'];
         $request_url = $end_point . '?' . http_build_query($search_file_request);
         
@@ -180,7 +183,7 @@ private function _doOnSuccess(SearchFilesResponse $response)
     {
         $this->_current_response = $response;
         $this->_api_in_progress = false;
-        
+
         if ($this->_initial_invalid_state) {
             $this->_initial_invalid_state = false;
         }
diff --git a/src/Request/AbstractRequest.php b/src/Request/AbstractRequest.php
new file mode 100644
index 0000000..7909e8c
--- /dev/null
+++ b/src/Request/AbstractRequest.php
@@ -0,0 +1,81 @@
+<?php
+/**
+ * Copyright 2017 Adobe Systems Incorporated. All rights reserved.
+ * This file is licensed to you under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License. You may obtain a copy
+ * of the License at http://www.apache.org/licenses/LICENSE-2.0
+ */
+
+namespace AdobeStock\Api\Request;
+
+use AdobeStock\Api\Exception\StockApi as StockApiException;
+
+/**
+ * Class AbstractRequest
+ */
+class AbstractRequest
+{
+    /**
+     * Language location code
+     *
+     * @var string
+     */
+    public $locale;
+
+    /**
+     * x-request-id header
+     *
+     * @var string
+     */
+    private $requestId;
+
+    /**
+     * Getter for Locale.
+     *
+     * @return string Language location code.
+     */
+    public function getLocale(): ?string
+    {
+        return $this->locale;
+    }
+
+    /**
+     * Setter for Locale.
+     *
+     * @param string $locale Language location code.
+     * @return AbstractRequest
+     * @throws StockApiException if locale is empty.
+     */
+    public function setLocale(string $locale) : AbstractRequest
+    {
+        if (!empty($locale)) {
+            $this->locale = $locale;
+        } else {
+            throw StockApiException::withMessage('Locale cannot be empty string');
+        }
+
+        return $this;
+    }
+
+    /**
+     * Set x-request-id header
+     *
+     * @param string $requestId
+     * @return AbstractRequest
+     */
+    public function setRequestId(string $requestId): AbstractRequest
+    {
+        $this->requestId = $requestId;
+        return $this;
+    }
+
+    /**
+     * Get x-request-id header
+     *
+     * @return string|null
+     */
+    public function getRequestId(): ?string
+    {
+        return $this->requestId;
+    }
+}
diff --git a/src/Request/License.php b/src/Request/License.php
index 0ecb26f..a3d4ab3 100644
--- a/src/Request/License.php
+++ b/src/Request/License.php
@@ -13,14 +13,8 @@
 use \AdobeStock\Api\Models\LicenseReference;
 use \AdobeStock\Api\Core\Constants as CoreConstants;
 
-class License
+class License extends AbstractRequest
 {
-    /**
-     * Language location code
-     * @var string
-     */
-    public $locale;
-    
     /**
      * Asset's unique identifer
      * @var int
@@ -53,32 +47,6 @@ class License
      */
     public $license_reference;
 
-    /**
-     * Getter for Locale.
-     * @return string Language location code.
-     */
-    public function getLocale(): string
-    {
-        return $this->locale;
-    }
-
-    /**
-     * Setter for Locale.
-     * @param string $locale Language location code.
-     * @return License
-     * @throws StockApiException if locale is empty.
-     */
-    public function setLocale(string $locale): License
-    {
-        if (!empty($locale)) {
-            $this->locale = $locale;
-        } else {
-            throw StockApiException::withMessage('Locale cannot be empty string');
-        }
-        
-        return $this;
-    }
-
     /**
      * Getter for ContentId.
      * @return int|null Asset identifier for an existing asset.
diff --git a/src/Request/LicenseHistory.php b/src/Request/LicenseHistory.php
index fca4d42..32f7acd 100644
--- a/src/Request/LicenseHistory.php
+++ b/src/Request/LicenseHistory.php
@@ -11,13 +11,8 @@
 use \AdobeStock\Api\Exception\StockApi as StockApiException;
 use \AdobeStock\Api\Models\SearchParamLicenseHistory as SearchParamLicenseHistoryModel;
 
-class LicenseHistory
+class LicenseHistory extends AbstractRequest
 {
-    /**
-     * @var string Language location code
-     */
-    public $locale;
-    
     /**
      * @var SearchParamLicenseHistoryModel search params.
      */
@@ -27,32 +22,7 @@ class LicenseHistory
      * @var array result column constants
      */
     public $result_columns;
-    
-    /**
-     * Getter for Locale.
-     * @return string|null Language location code.
-     */
-    public function getLocale() : ?string
-    {
-        return $this->locale;
-    }
-    
-    /**
-     * Setter for Locale.
-     * @param string $locale Language location code.
-     * @throws StockApiException if locale is null
-     * @return LicenseHistory
-     */
-    public function setLocale(string $locale = null) : LicenseHistory
-    {
-        if ($locale === null) {
-            throw StockApiException::withMessage('Locale cannot be null');
-        }
-        
-        $this->locale = $locale;
-        return $this;
-    }
-    
+
     /**
      * Get SearchParameters array that consists of various search params
      * @return SearchParamLicenseHistoryModel|null
diff --git a/src/Request/SearchCategory.php b/src/Request/SearchCategory.php
index 52083d5..3267da7 100644
--- a/src/Request/SearchCategory.php
+++ b/src/Request/SearchCategory.php
@@ -10,46 +10,14 @@
 
 use \AdobeStock\Api\Exception\StockApi as StockApiException;
 
-class SearchCategory
+class SearchCategory extends AbstractRequest
 {
-    /**
-     * Language location code
-     * @var string
-     */
-    public $locale;
-
     /**
      * Unique identifier for an existing category.
      * @var integer
      */
     public $category_id;
 
-    /**
-     * Getter for Locale.
-     * @return string Language location code.
-     */
-    public function getLocale()
-    {
-        return $this->locale;
-    }
-
-    /**
-     * Setter for Locale.
-     * @param string $locale Language location code.
-     * @return SearchCategory
-     * @throws StockApiException if locale is empty.
-     */
-    public function setLocale(string $locale) : SearchCategory
-    {
-        if (!empty($locale)) {
-            $this->locale = $locale;
-        } else {
-            throw StockApiException::withMessage('Locale cannot be empty string');
-        }
-
-        return $this;
-    }
-
     /**
      * Getter for CategoryId.
      * @return int|null Unique identifier for an existing category.
diff --git a/src/Request/SearchFiles.php b/src/Request/SearchFiles.php
index cf9fd29..c38cd4a 100644
--- a/src/Request/SearchFiles.php
+++ b/src/Request/SearchFiles.php
@@ -12,13 +12,8 @@
 use \AdobeStock\Api\Core\Constants as Constants;
 use \AdobeStock\Api\Models\SearchParameters as SearchParametersModel;
 
-class SearchFiles
+class SearchFiles extends AbstractRequest
 {
-    /**
-     * @var string Language location code
-     */
-    public $locale;
-    
     /**
      * @var SearchParametersModel search params.
      */
@@ -33,31 +28,7 @@ class SearchFiles
      * @var string Similar Image Path
      */
     public $similar_image;
-    
-    /**
-     * Getter for Locale.
-     * @return string|null Language location code.
-     */
-    public function getLocale() : ?string
-    {
-        return $this->locale;
-    }
-    
-    /**
-     * Setter for Locale.
-     * @param string $locale Language location code.
-     * @return SearchFiles
-     */
-    public function setLocale(string $locale = null) : SearchFiles
-    {
-        if ($locale == null) {
-            throw StockApiException::withMessage('Locale cannot be null');
-        }
-        
-        $this->locale = $locale;
-        return $this;
-    }
-    
+
     /**
      * Get SearchParameters array that consists of various search params
      * @return SearchParametersModel|null
diff --git a/test/src/Api/Client/LicenseFactoryTest.php b/test/src/Api/Client/LicenseFactoryTest.php
index d1bbe2a..533c5fa 100644
--- a/test/src/Api/Client/LicenseFactoryTest.php
+++ b/test/src/Api/Client/LicenseFactoryTest.php
@@ -316,6 +316,7 @@ public function getAbandonLicenseShouldThrowExceptionIfResponseCodeIsNot204()
      */
     public function downloadAssetRequestShouldReturnValidRequestObject()
     {
+        $url = 'https://primary.staging.adobestock.com/Rest/Libraries/Download/84071201/1';
         $response = [
             'member' =>
             [
@@ -335,11 +336,10 @@ public function downloadAssetRequestShouldReturnValidRequestObject()
                         'state' => 'purchased',
                         'license' => 'Standard',
                         'date' => '2017-06-21 10:38:52',
-                        'url' => 'https://primary.staging.adobestock.com/Rest/Libraries/Download/84071201/1',
+                        'url' => $url,
                         'content_type' => 'image/jpeg',
                         'width' => 4000,
                         'height' => 3928,
-                            
                     ],
                 ],
             ],
@@ -349,6 +349,7 @@ public function downloadAssetRequestShouldReturnValidRequestObject()
         $request = new LicenseRequest();
         $request->setContentId(84071201)->setLicenseState('STANDARD');
         $guzzle_request = $this->_license_factory->downloadAssetRequest($request, 'access_token', $this->_mocked_http_client);
+        $this->assertEquals($guzzle_request, new Request('GET', $url . '?token=access_token'));
     }
     
     /**
diff --git a/test/src/Api/Client/SearchFilesTest.php b/test/src/Api/Client/SearchFilesTest.php
new file mode 100644
index 0000000..bac5912
--- /dev/null
+++ b/test/src/Api/Client/SearchFilesTest.php
@@ -0,0 +1,65 @@
+<?php
+/**
+ * Copyright 2017 Adobe Systems Incorporated. All rights reserved.
+ * This file is licensed to you under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License. You may obtain a copy
+ * of the License at http://www.apache.org/licenses/LICENSE-2.0
+ */
+
+namespace AdobeStock\Api\Test;
+
+use AdobeStock\Api\Client\AdobeStock;
+use AdobeStock\Api\Models\SearchParameters;
+use AdobeStock\Api\Request\SearchFiles as SearchFilesRequest;
+use PHPUnit\Framework\TestCase;
+
+class SearchFilesTest extends TestCase
+{
+    /**
+     * Test SearchFiles with custom x-request-id header
+     */
+    public function testCustomRequestId()
+    {
+        $requestId = 'custom_request_id';
+
+        $stream_mock = $this->getMockBuilder(\GuzzleHttp\Psr7\Stream::class)
+            ->disableOriginalConstructor()
+            ->setMethods(['__toString'])
+            ->getMock();
+        $stream_mock->expects($this->once())
+            ->method('__toString')
+            ->willReturn('{"item": 1}');
+        $client_mock = $this->getMockBuilder(\AdobeStock\Api\Client\Http\HttpInterface::class)
+            ->setMethods(['doGet'])
+            ->getMockForAbstractClass();
+        $client_mock->expects($this->once())
+            ->method('doGet')
+            ->with(
+                $this->stringStartsWith('https://stock-stage.adobe.io/Rest/Media/1/Search/Files'),
+                [
+                    'headers' => [
+                        'x-api-key' => 'APIKey',
+                        'x-product' => 'Product',
+                        'Authorization' => null,
+                        'x-request-id' => $requestId
+                    ]
+                ]
+            )
+            ->willReturn($stream_mock);
+
+
+        $adobe_client = new AdobeStock('APIKey', 'Product', 'STAGE', $client_mock);
+        $request = new SearchFilesRequest();
+
+        $search_params = new SearchParameters();
+        $search_params->setWords('tree');
+
+        $request->setLocale('En_US');
+        $request->setSearchParams($search_params);
+        $request->setResultColumns(['id']);
+        $request->setRequestId($requestId);
+
+        $client = $adobe_client->searchFilesInitialize($request, 'access_token');
+        $client->getNextResponse();
+    }
+}
diff --git a/test/src/Api/Request/LicenseHistoryRequestTest.php b/test/src/Api/Request/LicenseHistoryRequestTest.php
index 17ef6a1..46e364b 100644
--- a/test/src/Api/Request/LicenseHistoryRequestTest.php
+++ b/test/src/Api/Request/LicenseHistoryRequestTest.php
@@ -67,7 +67,7 @@ public function setSearchParamsThrowException()
      */
     public function setLocaleThrowException()
     {
-        $this->_request->setLocale(null);
+        $this->_request->setLocale('');
     }
     
     /**
diff --git a/test/src/Api/Request/SearchFilesRequestTest.php b/test/src/Api/Request/SearchFilesRequestTest.php
index 64f3f83..3c7e3b7 100644
--- a/test/src/Api/Request/SearchFilesRequestTest.php
+++ b/test/src/Api/Request/SearchFilesRequestTest.php
@@ -16,7 +16,7 @@ class SearchFilesRequestTest extends TestCase
 {
     /**
      * Request object for search Files.
-     * @var SearchFiles
+     * @var SearchFilesRequest
      */
     private $_request;
     
@@ -50,7 +50,7 @@ public function testAllTheGettersSettersReturnandSetTheProperValue()
         $this->assertInstanceOf(SearchParametersModels::class, $this->_request->getSearchParams());
         $this->_request->setResultColumns($result_column_array);
         $this->assertEquals($result_column_array, $this->_request->getResultColumns());
-        $this->_request->setSimilarImage('test/resources/TestFile.png');
+        $this->_request->setSimilarImage($this->getAbsolutePath('test/resources/TestFile.png'));
     }
     
     /**
@@ -69,7 +69,7 @@ public function setSearchParamsThrowException()
      */
     public function setLocaleThrowException()
     {
-        $this->_request->setLocale(null);
+        $this->_request->setLocale('');
     }
     
     /**
@@ -89,4 +89,13 @@ public function setSimilarImageThrowExceptionIfFileDoesntExist()
     {
         $this->_request->setSimilarImage('');
     }
+
+    /**
+     * @param string $path
+     * @return string
+     */
+    private function getAbsolutePath(string $path): string
+    {
+        return dirname(dirname(dirname(dirname(__DIR__)))) . '/' . $path;
+    }
 }