diff --git a/src/Entity/ConnectionType.php b/src/Entity/ConnectionType.php
index 4b229d9394a631129f591ad4403c4b563498764f..c1585e2491e3ea482b4b85714a249d59e9410dd3 100644
--- a/src/Entity/ConnectionType.php
+++ b/src/Entity/ConnectionType.php
@@ -119,28 +119,28 @@ class ConnectionType extends ConfigEntityBase implements
   /**
    * {@inheritdoc}
    */
-  public function getApiId() {
+  public function getApiId(): ?string {
     return $this->api_id;
   }
 
   /**
    * {@inheritdoc}
    */
-  public function getApiVersion() {
+  public function getApiVersion(): ?string {
     return $this->api_version;
   }
 
   /**
    * {@inheritdoc}
    */
-  public function getBaseNamespace() {
+  public function getBaseNamespace(): ?string {
     return $this->base_namespace;
   }
 
   /**
    * {@inheritdoc}
    */
-  public function getAuthentication() {
+  public function getAuthentication(): ?array {
     return $this->authentication;
   }
 
diff --git a/src/Entity/ConnectionTypeInterface.php b/src/Entity/ConnectionTypeInterface.php
index b1d9d84199afbf8a1eaa4468f8e9444e7644d648..b4cd077ccf32fd48ccb75667b5baabaa1db9e2ab 100644
--- a/src/Entity/ConnectionTypeInterface.php
+++ b/src/Entity/ConnectionTypeInterface.php
@@ -23,7 +23,7 @@ interface ConnectionTypeInterface extends
    * @return string|null
    *   The ID, or NULL if it has not been defined.
    */
-  public function getApiId();
+  public function getApiId(): ?string;
 
   /**
    * Returns the version of the web service endpoint e.g. 22.200.001.
@@ -31,7 +31,7 @@ interface ConnectionTypeInterface extends
    * @return string|null
    *   The version, or NULL if it has not been defined.
    */
-  public function getApiVersion();
+  public function getApiVersion(): ?string;
 
   /**
    * Returns the base namespace of the API client.
@@ -45,7 +45,7 @@ interface ConnectionTypeInterface extends
    * @return string|null
    *   The namespace, or NULL if it has not been defined.
    */
-  public function getBaseNamespace();
+  public function getBaseNamespace(): ?string;
 
   /**
    * Returns the authentication settings.
@@ -56,6 +56,6 @@ interface ConnectionTypeInterface extends
    * @return array|null
    *   The authentication settings, or NULL if no settings have been defined.
    */
-  public function getAuthentication();
+  public function getAuthentication(): ?array;
 
 }