diff --git a/src/Model/PaginationResponse.php b/src/Model/PaginationResponse.php
index 470e216..42d297d 100644
--- a/src/Model/PaginationResponse.php
+++ b/src/Model/PaginationResponse.php
@@ -19,41 +19,25 @@ trait PaginationResponse
     /**
      * @var array
      */
-    protected $paging;
+    private $paging;
 
     public function getNextUrl(): ?string
     {
-        if (!isset($this->paging['next'])) {
-            return null;
-        }
-
-        return $this->paging['next'];
+        return $this->paging['next'] ?? null;
     }
 
     public function getPreviousUrl(): ?string
     {
-        if (!isset($this->paging['previous'])) {
-            return null;
-        }
-
-        return $this->paging['previous'];
+        return $this->paging['previous'] ?? null;
     }
 
     public function getFirstUrl(): ?string
     {
-        if (!isset($this->paging['first'])) {
-            return null;
-        }
-
-        return $this->paging['first'];
+        return $this->paging['first'] ?? null;
     }
 
     public function getLastUrl(): ?string
     {
-        if (!isset($this->paging['last'])) {
-            return null;
-        }
-
-        return $this->paging['last'];
+        return $this->paging['last'] ?? null;
     }
 }
diff --git a/src/Model/PagingProvider.php b/src/Model/PagingProvider.php
index ab79b15..be1e8ad 100644
--- a/src/Model/PagingProvider.php
+++ b/src/Model/PagingProvider.php
@@ -18,29 +18,21 @@ interface PagingProvider
 {
     /**
      * Returns the `$paging->next` URL.
-     *
-     * @return string
      */
-    public function getNextUrl();
+    public function getNextUrl(): ?string;
 
     /**
      * Returns the `$paging->prev` URL.
-     *
-     * @return string
      */
-    public function getPreviousUrl();
+    public function getPreviousUrl(): ?string;
 
     /**
      * Returns the `$paging->first` URL.
-     *
-     * @return string
      */
-    public function getFirstUrl();
+    public function getFirstUrl(): ?string;
 
     /**
      * Returns the `$paging->last` URL.
-     *
-     * @return string
      */
-    public function getLastUrl();
+    public function getLastUrl(): ?string;
 }