diff --git a/src/OpenConext/EngineBlock/Service/ReleaseAsEnforcer.php b/src/OpenConext/EngineBlock/Service/ReleaseAsEnforcer.php
index e4d6b306c..5bf33ade9 100644
--- a/src/OpenConext/EngineBlock/Service/ReleaseAsEnforcer.php
+++ b/src/OpenConext/EngineBlock/Service/ReleaseAsEnforcer.php
@@ -19,6 +19,7 @@
 namespace OpenConext\EngineBlock\Service;
 
 use Psr\Log\LoggerInterface;
+use function is_null;
 
 class ReleaseAsEnforcer implements ReleaseAsEnforcerInterface
 {
@@ -37,6 +38,29 @@ public function enforce(array $attributes, array $releaseAsOverrides)
     {
         foreach ($releaseAsOverrides as $oldAttributeName => $overrideValue) {
             $newAttributeName = $overrideValue[0]['release_as'];
+            if (!array_key_exists($oldAttributeName, $attributes)) {
+                $this->logger->warning(
+                    sprintf(
+                        'Releasing "%s" as "%s" is not possible, "%s" is not in assertion',
+                        $oldAttributeName,
+                        $newAttributeName,
+                        $oldAttributeName
+                    )
+                );
+                continue;
+            }
+            if (is_null($attributes[$oldAttributeName])) {
+                $this->logger->warning(
+                    sprintf(
+                        'Releasing "%s" as "%s" is not possible, value for "%s" is null',
+                        $oldAttributeName,
+                        $newAttributeName,
+                        $oldAttributeName
+                    )
+                );
+                unset($attributes[$oldAttributeName]);
+                continue;
+            }
             $attributeValue = $attributes[$oldAttributeName];
             unset($attributes[$oldAttributeName]);
             $this->logger->notice(
diff --git a/tests/unit/OpenConext/EngineBlock/Service/ReleaseAsEnforcerTest.php b/tests/unit/OpenConext/EngineBlock/Service/ReleaseAsEnforcerTest.php
index 6d2829342..f00ed4981 100644
--- a/tests/unit/OpenConext/EngineBlock/Service/ReleaseAsEnforcerTest.php
+++ b/tests/unit/OpenConext/EngineBlock/Service/ReleaseAsEnforcerTest.php
@@ -57,6 +57,18 @@ public function testEnforce($attributes, $releaseAsOverrides, $expectedResult, $
         }
     }
 
+
+    /**
+     * @dataProvider enforceDataProviderWarnings
+     */
+    public function testEnforceImpossible($attributes, $releaseAsOverrides, $expectedResult, $expectedLogMessage)
+    {
+
+        $this->logger->shouldReceive('warning')->with($expectedLogMessage);
+        $result = $this->enforcer->enforce($attributes, $releaseAsOverrides);
+        $this->assertEquals($expectedResult, $result);
+    }
+
     public function enforceDataProvider()
     {
         return [
@@ -88,6 +100,34 @@ public function enforceDataProvider()
                     'Releasing attribute "urn:mace:dir:attribute-def:cn" as "ComonNaam" as specified in the release_as ARP setting'
                 ]
             ],
+            'single attribute override, empty attribute value is allowed' => [
+                'attributes' => [
+                    "urn:mace:dir:attribute-def:displayName" => ["Ad Doe"],
+                    "urn:mace:dir:attribute-def:cn" => [],
+                    "urn:mace:dir:attribute-def:sn" => ["Doe"],
+                    "urn:mace:dir:attribute-def:givenName" => ["Ad"],
+                    "urn:mace:dir:attribute-def:mail" => ["ad@example.com"]
+                ],
+                'releaseAsOverrides' => [
+                    "urn:mace:dir:attribute-def:cn" => [
+                        [
+                            "value" => "*",
+                            "release_as" => "ComonNaam",
+                            "use_as_nameid" => false
+                        ]
+                    ]
+                ],
+                'expectedResult' => [
+                    "urn:mace:dir:attribute-def:displayName" => ["Ad Doe"],
+                    "urn:mace:dir:attribute-def:sn" => ["Doe"],
+                    "urn:mace:dir:attribute-def:givenName" => ["Ad"],
+                    "urn:mace:dir:attribute-def:mail" => ["ad@example.com"],
+                    "ComonNaam" => []
+                ],
+                'expectedLogMessages' => [
+                    'Releasing attribute "urn:mace:dir:attribute-def:cn" as "ComonNaam" as specified in the release_as ARP setting'
+                ]
+            ],
             'multiple attribute overrides' => [
                 'attributes' => [
                     "urn:mace:dir:attribute-def:displayName" => ["John Smith"],
@@ -141,4 +181,63 @@ public function enforceDataProvider()
             ],
         ];
     }
+
+    public function enforceDataProviderWarnings()
+    {
+        return [
+            'targeted attribute not in assertion' => [
+                'attributes' => [
+                    "urn:mace:dir:attribute-def:displayName" => ["Ad Doe"],
+                    "urn:mace:dir:attribute-def:cn" => ["Ad Doe"],
+                    "urn:mace:dir:attribute-def:sn" => ["Doe"],
+                    "urn:mace:dir:attribute-def:givenName" => ["Ad"],
+                    "urn:mace:dir:attribute-def:mail" => ["ad@example.com"],
+                ],
+                'releaseAsOverrides' => [
+                    "urn:mace:dir:attribute-def:eduPersonTargetedId" => [
+                        [
+                            "value" => "*",
+                            "release_as" => "UserName",
+                            "use_as_nameid" => false
+                        ]
+                    ]
+                ],
+                'expectedResult' => [
+                    "urn:mace:dir:attribute-def:displayName" => ["Ad Doe"],
+                    "urn:mace:dir:attribute-def:cn" => ["Ad Doe"],
+                    "urn:mace:dir:attribute-def:sn" => ["Doe"],
+                    "urn:mace:dir:attribute-def:givenName" => ["Ad"],
+                    "urn:mace:dir:attribute-def:mail" => ["ad@example.com"]
+                ],
+                'expectedLogMessages' => 'Releasing "urn:mace:dir:attribute-def:eduPersonTargetedId" as "UserName" is not possible, "urn:mace:dir:attribute-def:eduPersonTargetedId" is not in assertion'
+            ],
+            'targeted attribute value is set to null in assertion' => [
+                'attributes' => [
+                    "urn:mace:dir:attribute-def:displayName" => ["Ad Doe"],
+                    "urn:mace:dir:attribute-def:cn" => ["Ad Doe"],
+                    "urn:mace:dir:attribute-def:sn" => ["Doe"],
+                    "urn:mace:dir:attribute-def:eduPersonTargetedId" => null,
+                    "urn:mace:dir:attribute-def:givenName" => ["Ad"],
+                    "urn:mace:dir:attribute-def:mail" => ["ad@example.com"],
+                ],
+                'releaseAsOverrides' => [
+                    "urn:mace:dir:attribute-def:eduPersonTargetedId" => [
+                        [
+                            "value" => "*",
+                            "release_as" => "UserName",
+                            "use_as_nameid" => false
+                        ]
+                    ]
+                ],
+                'expectedResult' => [
+                    "urn:mace:dir:attribute-def:displayName" => ["Ad Doe"],
+                    "urn:mace:dir:attribute-def:cn" => ["Ad Doe"],
+                    "urn:mace:dir:attribute-def:sn" => ["Doe"],
+                    "urn:mace:dir:attribute-def:givenName" => ["Ad"],
+                    "urn:mace:dir:attribute-def:mail" => ["ad@example.com"]
+                ],
+                'expectedLogMessages' => 'Releasing "urn:mace:dir:attribute-def:eduPersonTargetedId" as "UserName" is not possible, value for "urn:mace:dir:attribute-def:eduPersonTargetedId" is null'
+            ],
+        ];
+    }
 }