diff --git a/app/BaseServiceProvider.php b/app/BaseServiceProvider.php
index 9c5ba00c..a0a626ca 100644
--- a/app/BaseServiceProvider.php
+++ b/app/BaseServiceProvider.php
@@ -31,7 +31,7 @@ protected function addShared(string $serviceName, callable $function, ?string $t
 
     /**
      * Get parameter from config
-     *
+     * @return mixed|null
      */
     protected function parameter(string $parameter)
     {
@@ -40,7 +40,7 @@ protected function parameter(string $parameter)
 
     /**
      * Get service from container
-     *
+     * @return object
      */
     protected function get(string $name)
     {
diff --git a/app/Console/AbstractMappingCommand.php b/app/Console/AbstractMappingCommand.php
index 87cdda0f..10ea985f 100644
--- a/app/Console/AbstractMappingCommand.php
+++ b/app/Console/AbstractMappingCommand.php
@@ -18,7 +18,7 @@ abstract class AbstractMappingCommand extends AbstractElasticSearchCommand
      */
     protected $documentType;
 
-    public function __construct(Client $client, $indexName, $documentType)
+    public function __construct(Client $client, string $indexName, string $documentType)
     {
         parent::__construct($client);
         $this->indexName = $indexName;
diff --git a/app/Console/AbstractReindexCommand.php b/app/Console/AbstractReindexCommand.php
index 4bbc9ca3..2e68c91f 100644
--- a/app/Console/AbstractReindexCommand.php
+++ b/app/Console/AbstractReindexCommand.php
@@ -63,14 +63,11 @@ public function __construct(
         $this->indexationStrategy = $indexationStrategy;
     }
 
-    /**
-     * @inheritdoc
-     */
     protected function runOperation(
         InputInterface $input,
         OutputInterface $output,
         AbstractReindexUDB3CoreOperation $operation
-    ) {
+    ): void {
         $indexationStrategy = $this->getIndexationStrategy();
         $logger = $this->getLogger($output);
 
diff --git a/phpstan.neon b/phpstan.neon
index 1c1d972a..4a08b7dd 100644
--- a/phpstan.neon
+++ b/phpstan.neon
@@ -1,5 +1,7 @@
 parameters:
-	level: 5
+	level: 6
+	checkMissingIterableValueType: false
+	checkGenericClassInNonGenericObjectType: false
 	paths:
 		- app
 		- src
diff --git a/src/Deserializer/DeserializerInterface.php b/src/Deserializer/DeserializerInterface.php
index f536bab2..c84338c7 100644
--- a/src/Deserializer/DeserializerInterface.php
+++ b/src/Deserializer/DeserializerInterface.php
@@ -6,5 +6,6 @@
 
 interface DeserializerInterface
 {
+    // @phpstan-ignore-next-line
     public function deserialize(string $data);
 }
diff --git a/src/ElasticSearch/AbstractElasticSearchQueryBuilder.php b/src/ElasticSearch/AbstractElasticSearchQueryBuilder.php
index c18f4c51..12683056 100644
--- a/src/ElasticSearch/AbstractElasticSearchQueryBuilder.php
+++ b/src/ElasticSearch/AbstractElasticSearchQueryBuilder.php
@@ -276,6 +276,10 @@ protected function withRangeQuery(string $fieldName, $from = null, $to = null)
         return $c;
     }
 
+    /**
+     * @param string|int|null $from
+     * @param string|int|null $to
+     */
     protected function createRangeQuery(string $fieldName, $from = null, $to = null): ?RangeQuery
     {
         $parameters = array_filter(
diff --git a/src/ElasticSearch/IndexationStrategy/IndexationStrategy.php b/src/ElasticSearch/IndexationStrategy/IndexationStrategy.php
index cce60dd4..dd8b6398 100644
--- a/src/ElasticSearch/IndexationStrategy/IndexationStrategy.php
+++ b/src/ElasticSearch/IndexationStrategy/IndexationStrategy.php
@@ -12,7 +12,7 @@ public function indexDocument(
         string $indexName,
         string $documentType,
         JsonDocument $jsonDocument
-    );
+    ): void;
 
     public function finish(): void;
 }
diff --git a/src/ElasticSearch/Operations/AbstractReindexUDB3CoreOperation.php b/src/ElasticSearch/Operations/AbstractReindexUDB3CoreOperation.php
index 7f47e13d..a4b4f237 100644
--- a/src/ElasticSearch/Operations/AbstractReindexUDB3CoreOperation.php
+++ b/src/ElasticSearch/Operations/AbstractReindexUDB3CoreOperation.php
@@ -4,6 +4,7 @@
 
 namespace CultuurNet\UDB3\Search\ElasticSearch\Operations;
 
+use Broadway\Serializer\Serializable;
 use Exception;
 use Broadway\Domain\DomainEventStream;
 use Broadway\Domain\DomainMessage;
@@ -166,7 +167,7 @@ private function dispatchEventForHit(array $hit): void
     }
 
 
-    private function getReadableEventType($event): string
+    private function getReadableEventType(Serializable $event): string
     {
         $parts = explode('\\', get_class($event));
         return end($parts);
diff --git a/src/ElasticSearch/Validation/ElasticSearchResponseValidatorInterface.php b/src/ElasticSearch/Validation/ElasticSearchResponseValidatorInterface.php
index ed45520a..5761cada 100644
--- a/src/ElasticSearch/Validation/ElasticSearchResponseValidatorInterface.php
+++ b/src/ElasticSearch/Validation/ElasticSearchResponseValidatorInterface.php
@@ -12,5 +12,5 @@ interface ElasticSearchResponseValidatorInterface
      *
      * @throws InvalidElasticSearchResponseException
      */
-    public function validate(array $responseData);
+    public function validate(array $responseData): void;
 }
diff --git a/src/Http/ApiRequestInterface.php b/src/Http/ApiRequestInterface.php
index 4db50515..a9fe7965 100644
--- a/src/Http/ApiRequestInterface.php
+++ b/src/Http/ApiRequestInterface.php
@@ -17,6 +17,10 @@
  */
 interface ApiRequestInterface extends ServerRequestInterface
 {
+    /**
+     * @param mixed|null $default
+     * @return mixed|null
+     */
     public function getQueryParam(string $name, $default = null);
 
     public function hasQueryParam(string $name): bool;
@@ -25,5 +29,9 @@ public function getQueryParamsKeys(): ?array;
 
     public function getQueryParameterBag(): ParameterBagInterface;
 
+    /**
+     * @param mixed|null $default
+     * @return mixed|null
+     */
     public function getServerParam(string $name, $default = null);
 }
diff --git a/src/Http/Authentication/Auth0/Auth0MetadataGenerator.php b/src/Http/Authentication/Auth0/Auth0MetadataGenerator.php
index 3558683c..7f5e0de7 100644
--- a/src/Http/Authentication/Auth0/Auth0MetadataGenerator.php
+++ b/src/Http/Authentication/Auth0/Auth0MetadataGenerator.php
@@ -9,17 +9,17 @@
 use GuzzleHttp\Client;
 use GuzzleHttp\Exception\ConnectException;
 use GuzzleHttp\Psr7\Request;
-use Psr\Log\LoggerAwareTrait;
+use Psr\Log\LoggerInterface;
 use Psr\Log\NullLogger;
 
 final class Auth0MetadataGenerator implements MetadataGenerator
 {
-    use LoggerAwareTrait;
-
     private Client $client;
 
     private string $domain;
 
+    private LoggerInterface $logger;
+
     public function __construct(
         Client $client,
         string $domain
@@ -56,4 +56,9 @@ public function get(string $clientId, string $token): ?array
         $res = Json::decodeAssociatively($response->getBody()->getContents());
         return $res['client_metadata'] ?? [];
     }
+
+    public function setLogger(LoggerInterface $logger): void
+    {
+        $this->logger = $logger;
+    }
 }
diff --git a/src/Http/Authentication/Keycloak/KeycloakMetadataGenerator.php b/src/Http/Authentication/Keycloak/KeycloakMetadataGenerator.php
index 30a12e52..5f8ce069 100644
--- a/src/Http/Authentication/Keycloak/KeycloakMetadataGenerator.php
+++ b/src/Http/Authentication/Keycloak/KeycloakMetadataGenerator.php
@@ -10,16 +10,15 @@
 use GuzzleHttp\Exception\ConnectException;
 use GuzzleHttp\Psr7\Request;
 use GuzzleHttp\Psr7\Uri;
-use Psr\Log\LoggerAwareTrait;
+use Psr\Log\LoggerInterface;
 use Psr\Log\NullLogger;
 
 final class KeycloakMetadataGenerator implements MetadataGenerator
 {
-    use LoggerAwareTrait;
-
     private Client $client;
     private string $domain;
     private string $realm;
+    private LoggerInterface $logger;
 
     public function __construct(
         Client $client,
@@ -94,4 +93,9 @@ private function convertDefaultScopes(array $defaultScopes): array
         $result['publiq-apis'] = implode(' ', $scopes);
         return $result;
     }
+
+    public function setLogger(LoggerInterface $logger): void
+    {
+        $this->logger = $logger;
+    }
 }
diff --git a/src/Http/Authentication/MetadataGenerator.php b/src/Http/Authentication/MetadataGenerator.php
index 62dcc702..678fceec 100644
--- a/src/Http/Authentication/MetadataGenerator.php
+++ b/src/Http/Authentication/MetadataGenerator.php
@@ -10,5 +10,5 @@ interface MetadataGenerator
 {
     public function get(string $clientId, string $token): ?array;
 
-    public function setLogger(LoggerInterface $logger);
+    public function setLogger(LoggerInterface $logger): void;
 }
diff --git a/src/Http/Parameters/ArrayParameterBagAdapter.php b/src/Http/Parameters/ArrayParameterBagAdapter.php
index a091ccf6..8e124c99 100644
--- a/src/Http/Parameters/ArrayParameterBagAdapter.php
+++ b/src/Http/Parameters/ArrayParameterBagAdapter.php
@@ -85,10 +85,10 @@ public function getIntegerFromParameter(
     }
 
     public function getExplodedStringFromParameter(
-        $parameterName,
-        $defaultValueAsString = null,
+        string $parameterName,
+        ?string $defaultValueAsString = null,
         callable $callback = null,
-        $delimiter = ','
+        string $delimiter = ','
     ): array {
         $callback = $this->ensureCallback($callback);
 
@@ -148,10 +148,13 @@ public function getDateTimeFromParameter(string $queryParameter, ?string $defaul
         return $this->getStringFromParameter($queryParameter, $defaultValueAsString, $callback);
     }
 
-    private function get(string $queryParameter, $default = null)
+    /**
+     * @return mixed|null
+     */
+    private function get(string $queryParameter)
     {
         if (!isset($this->parameterBag[$queryParameter])) {
-            return $default;
+            return null;
         }
 
         return $this->parameterBag[$queryParameter];
diff --git a/src/Http/ResponseFactory.php b/src/Http/ResponseFactory.php
index d1399c5d..dcf6aabe 100644
--- a/src/Http/ResponseFactory.php
+++ b/src/Http/ResponseFactory.php
@@ -30,6 +30,9 @@ public static function apiProblem($data, int $code = StatusCodeInterface::STATUS
         return self::jsonWithCustomContentType('application/problem+json', $data, $code);
     }
 
+    /**
+     * @param array|object $data
+     */
     private static function jsonWithCustomContentType(
         string $contentType,
         $data,
diff --git a/src/Json.php b/src/Json.php
index 57848b57..834e79bf 100644
--- a/src/Json.php
+++ b/src/Json.php
@@ -65,7 +65,7 @@ public static function encodeForHttpResponse($value): string
      * @param string $data
      *   Encoded JSON data.
      *
-     * @returns mixed
+     * @return mixed|null
      *   Decoded data, usually as an array or stdClass object but can also be a string, integer, boolean, etc depending
      *   on the encoded data.
      *
@@ -81,7 +81,7 @@ public static function decode(string $data)
      * @param string $data
      *   Encoded JSON data.
      *
-     * @returns mixed
+     * @return mixed|null
      *   Decoded data, usually as an array but can also be a string, integer, boolean, etc depending on the encoded
      *   data.
      *
diff --git a/src/ReadModel/DocumentGone.php b/src/ReadModel/DocumentGone.php
index 19dab42a..ee14ebb2 100644
--- a/src/ReadModel/DocumentGone.php
+++ b/src/ReadModel/DocumentGone.php
@@ -9,7 +9,7 @@
 
 final class DocumentGone extends RuntimeException
 {
-    public function __construct($message = '', $code = 410, Exception $previous = null)
+    public function __construct(string $message = '', int $code = 410, Exception $previous = null)
     {
         parent::__construct($message, $code, $previous);
     }
diff --git a/src/ReadModel/JsonDocument.php b/src/ReadModel/JsonDocument.php
index eaabe681..822c4267 100644
--- a/src/ReadModel/JsonDocument.php
+++ b/src/ReadModel/JsonDocument.php
@@ -35,6 +35,9 @@ public function getRawBody(): string
         return $this->body;
     }
 
+    /**
+     * @param object|array $body
+     */
     public function withBody($body): JsonDocument
     {
         return new self($this->id, Json::encode($body));
diff --git a/tests/ElasticSearch/Operations/AbstractOperationTestCase.php b/tests/ElasticSearch/Operations/AbstractOperationTestCase.php
index 7e20688f..8768fbd3 100644
--- a/tests/ElasticSearch/Operations/AbstractOperationTestCase.php
+++ b/tests/ElasticSearch/Operations/AbstractOperationTestCase.php
@@ -27,7 +27,7 @@ abstract class AbstractOperationTestCase extends TestCase
      */
     protected $logger;
 
-
+    // @phpstan-ignore-next-line
     protected $operation;
 
     protected function setUp(): void
@@ -43,5 +43,6 @@ protected function setUp(): void
         $this->operation = $this->createOperation($this->client, $this->logger);
     }
 
+    // @phpstan-ignore-next-line
     abstract protected function createOperation(Client $client, LoggerInterface $logger);
 }
diff --git a/tests/Http/OfferSearchControllerTest.php b/tests/Http/OfferSearchControllerTest.php
index dbd6c43f..e360cf55 100644
--- a/tests/Http/OfferSearchControllerTest.php
+++ b/tests/Http/OfferSearchControllerTest.php
@@ -675,6 +675,7 @@ public function it_works_with_a_min_price_and_max_price_if_no_exact_price_is_set
 
     /**
      * @test
+     * @param bool|string|int $stringValue
      * @dataProvider booleanStringDataProvider
      */
     public function it_converts_the_media_objects_toggle_parameter_to_a_correct_boolean(
@@ -704,6 +705,7 @@ public function it_converts_the_media_objects_toggle_parameter_to_a_correct_bool
 
     /**
      * @test
+     * @param bool|string|int $stringValue
      * @dataProvider booleanStringDataProvider
      */
     public function it_converts_the_uitpas_toggle_parameter_to_a_correct_boolean(
@@ -907,6 +909,7 @@ public function it_transforms_the_request_address_country_to_uppercase(): void
     /**
      * @test
      * @dataProvider malformedDateTimeProvider
+     * @param bool|string|int $malformedDateTimeAsString
      * @todo PHP8 upgrade: change Type hint to string|bool
      */
     public function it_throws_an_exception_for_a_malformed_date_from($malformedDateTimeAsString): void
diff --git a/tests/Http/Parameters/ArrayParameterBagAdapterTest.php b/tests/Http/Parameters/ArrayParameterBagAdapterTest.php
index e7670ee6..63c2039f 100644
--- a/tests/Http/Parameters/ArrayParameterBagAdapterTest.php
+++ b/tests/Http/Parameters/ArrayParameterBagAdapterTest.php
@@ -308,8 +308,8 @@ public function it_should_return_an_empty_array_for_a_delimited_string_parameter
 
     /**
      * @test
+     * @param bool|string|int $parameterValue
      * @dataProvider booleanDataProvider
-     *
      */
     public function it_should_parse_a_boolean_value_from_a_parameter(
         $parameterValue,