diff --git a/src/Glassboxx/Config.php b/src/Glassboxx/Config.php
index 68f297c..1f7a16a 100644
--- a/src/Glassboxx/Config.php
+++ b/src/Glassboxx/Config.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Opdavies\Glassboxx;
 
 class Config
diff --git a/src/Glassboxx/Request/AbstractRequest.php b/src/Glassboxx/Request/AbstractRequest.php
index b4a2d1f..173f849 100644
--- a/src/Glassboxx/Request/AbstractRequest.php
+++ b/src/Glassboxx/Request/AbstractRequest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Opdavies\Glassboxx\Request;
 
 abstract class AbstractRequest
diff --git a/src/Glassboxx/Request/AuthTokenRequest.php b/src/Glassboxx/Request/AuthTokenRequest.php
index a898c3d..02afbee 100644
--- a/src/Glassboxx/Request/AuthTokenRequest.php
+++ b/src/Glassboxx/Request/AuthTokenRequest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Opdavies\Glassboxx\Request;
 
 use Opdavies\Glassboxx\Config;
diff --git a/tests/Glassboxx/ConfigTest.php b/tests/Glassboxx/ConfigTest.php
index 2fea320..f391e51 100644
--- a/tests/Glassboxx/ConfigTest.php
+++ b/tests/Glassboxx/ConfigTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Opdavies\Glassboxx\Tests\Glassboxx;
 
 use Opdavies\Glassboxx\Config;
diff --git a/tests/Glassboxx/Request/AuthTokenRequestTest.php b/tests/Glassboxx/Request/AuthTokenRequestTest.php
index 6229e9b..b1baefe 100644
--- a/tests/Glassboxx/Request/AuthTokenRequestTest.php
+++ b/tests/Glassboxx/Request/AuthTokenRequestTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Opdavies\Glassboxx\Tests\Glassboxx\Request;
 
 use Opdavies\Glassboxx\Config;