diff --git a/src/Models/Permission.php b/src/Models/Permission.php
index 95df94fb..d23d15ac 100644
--- a/src/Models/Permission.php
+++ b/src/Models/Permission.php
@@ -86,7 +86,7 @@ public function users(): BelongsToMany
      *
      * @throws PermissionDoesNotExist
      */
-    public static function findByName(string $name, string $guardName = null): PermissionContract
+    public static function findByName(string $name, ?string $guardName = null): PermissionContract
     {
         $guardName = $guardName ?? Guard::getDefaultName(static::class);
         $permission = static::getPermission(['name' => $name, 'guard_name' => $guardName]);
@@ -104,7 +104,7 @@ public static function findByName(string $name, string $guardName = null): Permi
      *
      * @throws PermissionDoesNotExist
      */
-    public static function findById(int|string $id, string $guardName = null): PermissionContract
+    public static function findById(int|string $id, ?string $guardName = null): PermissionContract
     {
         $guardName = $guardName ?? Guard::getDefaultName(static::class);
         $permission = static::getPermission([(new static())->getKeyName() => $id, 'guard_name' => $guardName]);
@@ -121,7 +121,7 @@ public static function findById(int|string $id, string $guardName = null): Permi
      *
      * @return PermissionContract|Permission
      */
-    public static function findOrCreate(string $name, string $guardName = null): PermissionContract
+    public static function findOrCreate(string $name, ?string $guardName = null): PermissionContract
     {
         $guardName = $guardName ?? Guard::getDefaultName(static::class);
         $permission = static::getPermission(['name' => $name, 'guard_name' => $guardName]);
diff --git a/src/Models/Role.php b/src/Models/Role.php
index 4fd6e782..4b2e48ff 100644
--- a/src/Models/Role.php
+++ b/src/Models/Role.php
@@ -95,7 +95,7 @@ public function users(): BelongsToMany
      *
      * @throws RoleDoesNotExist
      */
-    public static function findByName(string $name, string $guardName = null): RoleContract
+    public static function findByName(string $name, ?string $guardName = null): RoleContract
     {
         $guardName = $guardName ?? Guard::getDefaultName(static::class);
 
@@ -113,7 +113,7 @@ public static function findByName(string $name, string $guardName = null): RoleC
      *
      * @return RoleContract|Role
      */
-    public static function findById(int|string $id, string $guardName = null): RoleContract
+    public static function findById(int|string $id, ?string $guardName = null): RoleContract
     {
         $guardName = $guardName ?? Guard::getDefaultName(static::class);
 
@@ -131,7 +131,7 @@ public static function findById(int|string $id, string $guardName = null): RoleC
      *
      * @return RoleContract|Role
      */
-    public static function findOrCreate(string $name, string $guardName = null): RoleContract
+    public static function findOrCreate(string $name, ?string $guardName = null): RoleContract
     {
         $guardName = $guardName ?? Guard::getDefaultName(static::class);
 
@@ -176,7 +176,7 @@ protected static function findByParam(array $params = []): ?RoleContract
      *
      * @throws PermissionDoesNotExist|GuardDoesNotMatch
      */
-    public function hasPermissionTo($permission, string $guardName = null): bool
+    public function hasPermissionTo($permission, ?string $guardName = null): bool
     {
         if ($this->getWildcardClass()) {
             return $this->hasWildcardPermission($permission, $guardName);
diff --git a/src/PermissionRegistrar.php b/src/PermissionRegistrar.php
index 3c3b0d7f..1300def8 100644
--- a/src/PermissionRegistrar.php
+++ b/src/PermissionRegistrar.php
@@ -145,7 +145,7 @@ public function forgetCachedPermissions()
         return $this->cache->forget($this->cacheKey);
     }
 
-    public function forgetWildcardPermissionIndex(Model $record = null): void
+    public function forgetWildcardPermissionIndex(?Model $record = null): void
     {
         if ($record) {
             unset($this->wildcardPermissionsIndex[get_class($record)][$record->getKey()]);
diff --git a/src/Traits/HasRoles.php b/src/Traits/HasRoles.php
index a8f183c0..97f87ba9 100644
--- a/src/Traits/HasRoles.php
+++ b/src/Traits/HasRoles.php
@@ -218,7 +218,7 @@ public function syncRoles(...$roles)
      *
      * @param  string|int|array|Role|Collection|\BackedEnum  $roles
      */
-    public function hasRole($roles, string $guard = null): bool
+    public function hasRole($roles, ?string $guard = null): bool
     {
         $this->loadMissing('roles');
 
@@ -282,7 +282,7 @@ public function hasAnyRole(...$roles): bool
      *
      * @param  string|array|Role|Collection|\BackedEnum  $roles
      */
-    public function hasAllRoles($roles, string $guard = null): bool
+    public function hasAllRoles($roles, ?string $guard = null): bool
     {
         $this->loadMissing('roles');
 
@@ -324,7 +324,7 @@ public function hasAllRoles($roles, string $guard = null): bool
      *
      * @param  string|array|Role|Collection  $roles
      */
-    public function hasExactRoles($roles, string $guard = null): bool
+    public function hasExactRoles($roles, ?string $guard = null): bool
     {
         $this->loadMissing('roles');