diff --git a/src/Contracts/QueryCacheModuleInterface.php b/src/Contracts/QueryCacheModuleInterface.php
index 78a7f0d..0458986 100644
--- a/src/Contracts/QueryCacheModuleInterface.php
+++ b/src/Contracts/QueryCacheModuleInterface.php
@@ -12,7 +12,7 @@ interface QueryCacheModuleInterface
      * @param  string|null  $appends
      * @return string
      */
-    public function generatePlainCacheKey(string $method = 'get', string $id = null, string $appends = null): string;
+    public function generatePlainCacheKey(string $method = 'get', ?string $id = null, ?string $appends = null): string;
 
     /**
      * Get the query cache callback.
@@ -22,5 +22,5 @@ public function generatePlainCacheKey(string $method = 'get', string $id = null,
      * @param  string|null  $id
      * @return \Closure
      */
-    public function getQueryCacheCallback(string $method = 'get', $columns = ['*'], string $id = null);
+    public function getQueryCacheCallback(string $method = 'get', $columns = ['*'], ?string $id = null);
 }
diff --git a/src/FlushQueryCacheObserver.php b/src/FlushQueryCacheObserver.php
index 7ca7ce2..f99cc43 100644
--- a/src/FlushQueryCacheObserver.php
+++ b/src/FlushQueryCacheObserver.php
@@ -3,6 +3,7 @@
 namespace Rennokki\QueryCache;
 
 use Exception;
+use Illuminate\Database\Eloquent\Collection;
 use Illuminate\Database\Eloquent\Model;
 
 class FlushQueryCacheObserver
@@ -150,7 +151,7 @@ public function morphToManyUpdatedExistingPivot($relation, Model $model, $ids)
      *
      * @throws Exception
      */
-    protected function invalidateCache(Model $model, $relation = null, $pivotedModels = null): void
+    protected function invalidateCache(Model $model, ?string $relation = null, ?Collection $pivotedModels = null): void
     {
         $class = get_class($model);
 
diff --git a/src/Traits/QueryCacheModule.php b/src/Traits/QueryCacheModule.php
index 79caa36..1eccc98 100644
--- a/src/Traits/QueryCacheModule.php
+++ b/src/Traits/QueryCacheModule.php
@@ -69,7 +69,7 @@ trait QueryCacheModule
      * @param  string|null  $id
      * @return array
      */
-    public function getFromQueryCache(string $method = 'get', array $columns = ['*'], string $id = null)
+    public function getFromQueryCache(string $method = 'get', array $columns = ['*'], ?string $id = null)
     {
         if (is_null($this->columns)) {
             $this->columns = $columns;
@@ -95,7 +95,7 @@ public function getFromQueryCache(string $method = 'get', array $columns = ['*']
      * @param  string|null  $id
      * @return \Closure
      */
-    public function getQueryCacheCallback(string $method = 'get', $columns = ['*'], string $id = null)
+    public function getQueryCacheCallback(string $method = 'get', $columns = ['*'], ?string $id = null)
     {
         return function () use ($method, $columns) {
             $this->avoidCache = true;
@@ -112,7 +112,7 @@ public function getQueryCacheCallback(string $method = 'get', $columns = ['*'],
      * @param  string|null  $appends
      * @return string
      */
-    public function getCacheKey(string $method = 'get', string $id = null, string $appends = null): string
+    public function getCacheKey(string $method = 'get', ?string $id = null, ?string $appends = null): string
     {
         $key = $this->generateCacheKey($method, $id, $appends);
         $prefix = $this->getCachePrefix();
@@ -128,7 +128,7 @@ public function getCacheKey(string $method = 'get', string $id = null, string $a
      * @param  string|null  $appends
      * @return string
      */
-    public function generateCacheKey(string $method = 'get', string $id = null, string $appends = null): string
+    public function generateCacheKey(string $method = 'get', ?string $id = null, ?string $appends = null): string
     {
         $key = $this->generatePlainCacheKey($method, $id, $appends);
 
@@ -147,7 +147,7 @@ public function generateCacheKey(string $method = 'get', string $id = null, stri
      * @param  string|null  $appends
      * @return string
      */
-    public function generatePlainCacheKey(string $method = 'get', string $id = null, string $appends = null): string
+    public function generatePlainCacheKey(string $method = 'get', ?string $id = null, ?string $appends = null): string
     {
         $name = $this->connection->getName();
 
diff --git a/src/Traits/QueryCacheable.php b/src/Traits/QueryCacheable.php
index c9f85a8..91bb85d 100644
--- a/src/Traits/QueryCacheable.php
+++ b/src/Traits/QueryCacheable.php
@@ -2,6 +2,7 @@
 
 namespace Rennokki\QueryCache\Traits;
 
+use Illuminate\Database\Eloquent\Collection;
 use Rennokki\QueryCache\FlushQueryCacheObserver;
 use Rennokki\QueryCache\Query\Builder;
 
@@ -68,7 +69,7 @@ protected function getCacheBaseTags(): array
      * @param  \Illuminate\Database\Eloquent\Collection|null  $pivotedModels
      * @return array
      */
-    public function getCacheTagsToInvalidateOnUpdate($relation = null, $pivotedModels = null): array
+    public function getCacheTagsToInvalidateOnUpdate(?string $relation = null, ?Collection $pivotedModels = null): array
     {
         /** @var \Illuminate\Database\Eloquent\Model $this */
         return $this->getCacheBaseTags();