diff --git a/lib/PhpParser/Node/Expr/ArrowFunction.php b/lib/PhpParser/Node/Expr/ArrowFunction.php
index 98e24a51..f9b4ec36 100644
--- a/lib/PhpParser/Node/Expr/ArrowFunction.php
+++ b/lib/PhpParser/Node/Expr/ArrowFunction.php
@@ -30,7 +30,7 @@ class ArrowFunction extends Expr implements FunctionLike {
      *     static?: bool,
      *     byRef?: bool,
      *     params?: Node\Param[],
-     *     returnType?: null|string|Node\Identifier|Node\Name|Node\ComplexType,
+     *     returnType?: null|Node\Identifier|Node\Name|Node\ComplexType,
      *     attrGroups?: Node\AttributeGroup[]
      * } $subNodes Array of the following subnodes:
      *             'expr'                  : Expression body
@@ -46,8 +46,7 @@ class ArrowFunction extends Expr implements FunctionLike {
         $this->static = $subNodes['static'] ?? false;
         $this->byRef = $subNodes['byRef'] ?? false;
         $this->params = $subNodes['params'] ?? [];
-        $returnType = $subNodes['returnType'] ?? null;
-        $this->returnType = \is_string($returnType) ? new Node\Identifier($returnType) : $returnType;
+        $this->returnType = $subNodes['returnType'] ?? null;
         $this->expr = $subNodes['expr'];
         $this->attrGroups = $subNodes['attrGroups'] ?? [];
     }
diff --git a/lib/PhpParser/Node/Expr/Closure.php b/lib/PhpParser/Node/Expr/Closure.php
index ee257d49..ddb4e0b7 100644
--- a/lib/PhpParser/Node/Expr/Closure.php
+++ b/lib/PhpParser/Node/Expr/Closure.php
@@ -31,7 +31,7 @@ class Closure extends Expr implements FunctionLike {
      *     byRef?: bool,
      *     params?: Node\Param[],
      *     uses?: ClosureUse[],
-     *     returnType?: null|string|Node\Identifier|Node\Name|Node\ComplexType,
+     *     returnType?: null|Node\Identifier|Node\Name|Node\ComplexType,
      *     stmts?: Node\Stmt[],
      *     attrGroups?: Node\AttributeGroup[],
      * } $subNodes Array of the following optional subnodes:
@@ -50,8 +50,7 @@ class Closure extends Expr implements FunctionLike {
         $this->byRef = $subNodes['byRef'] ?? false;
         $this->params = $subNodes['params'] ?? [];
         $this->uses = $subNodes['uses'] ?? [];
-        $returnType = $subNodes['returnType'] ?? null;
-        $this->returnType = \is_string($returnType) ? new Node\Identifier($returnType) : $returnType;
+        $this->returnType = $subNodes['returnType'] ?? null;
         $this->stmts = $subNodes['stmts'] ?? [];
         $this->attrGroups = $subNodes['attrGroups'] ?? [];
     }
diff --git a/lib/PhpParser/Node/NullableType.php b/lib/PhpParser/Node/NullableType.php
index e86d0974..847b6573 100644
--- a/lib/PhpParser/Node/NullableType.php
+++ b/lib/PhpParser/Node/NullableType.php
@@ -2,6 +2,8 @@
 
 namespace PhpParser\Node;
 
+use PhpParser\Node;
+
 class NullableType extends ComplexType {
     /** @var Identifier|Name Type */
     public $type;
@@ -9,12 +11,12 @@ class NullableType extends ComplexType {
     /**
      * Constructs a nullable type (wrapping another type).
      *
-     * @param string|Identifier|Name $type       Type
+     * @param Identifier|Name $type Type
      * @param array<string, mixed> $attributes Additional attributes
      */
-    public function __construct($type, array $attributes = []) {
+    public function __construct(Node $type, array $attributes = []) {
         $this->attributes = $attributes;
-        $this->type = \is_string($type) ? new Identifier($type) : $type;
+        $this->type = $type;
     }
 
     public function getSubNodeNames(): array {
diff --git a/lib/PhpParser/Node/Param.php b/lib/PhpParser/Node/Param.php
index ef110531..0732c574 100644
--- a/lib/PhpParser/Node/Param.php
+++ b/lib/PhpParser/Node/Param.php
@@ -3,6 +3,7 @@
 namespace PhpParser\Node;
 
 use PhpParser\Modifiers;
+use PhpParser\Node;
 use PhpParser\NodeAbstract;
 
 class Param extends NodeAbstract {
@@ -26,7 +27,7 @@ class Param extends NodeAbstract {
      *
      * @param Expr\Variable|Expr\Error                $var        Parameter variable
      * @param null|Expr                               $default    Default value
-     * @param null|string|Identifier|Name|ComplexType $type       Type declaration
+     * @param null|Identifier|Name|ComplexType $type Type declaration
      * @param bool                                    $byRef      Whether is passed by reference
      * @param bool                                    $variadic   Whether this is a variadic argument
      * @param array<string, mixed> $attributes Additional attributes
@@ -34,14 +35,14 @@ class Param extends NodeAbstract {
      * @param list<AttributeGroup> $attrGroups PHP attribute groups
      */
     public function __construct(
-        $var, ?Expr $default = null, $type = null,
+        $var, ?Expr $default = null, ?Node $type = null,
         bool $byRef = false, bool $variadic = false,
         array $attributes = [],
         int $flags = 0,
         array $attrGroups = []
     ) {
         $this->attributes = $attributes;
-        $this->type = \is_string($type) ? new Identifier($type) : $type;
+        $this->type = $type;
         $this->byRef = $byRef;
         $this->variadic = $variadic;
         $this->var = $var;
diff --git a/lib/PhpParser/Node/Stmt/ClassConst.php b/lib/PhpParser/Node/Stmt/ClassConst.php
index 44f0cc31..a5e467ab 100644
--- a/lib/PhpParser/Node/Stmt/ClassConst.php
+++ b/lib/PhpParser/Node/Stmt/ClassConst.php
@@ -22,20 +22,20 @@ class ClassConst extends Node\Stmt {
      * @param int $flags Modifiers
      * @param array<string, mixed> $attributes Additional attributes
      * @param list<Node\AttributeGroup> $attrGroups PHP attribute groups
-     * @param null|string|Node\Identifier|Node\Name|Node\ComplexType $type Type declaration
+     * @param null|Node\Identifier|Node\Name|Node\ComplexType $type Type declaration
      */
     public function __construct(
         array $consts,
         int $flags = 0,
         array $attributes = [],
         array $attrGroups = [],
-        $type = null
+        ?Node $type = null
     ) {
         $this->attributes = $attributes;
         $this->flags = $flags;
         $this->consts = $consts;
         $this->attrGroups = $attrGroups;
-        $this->type = \is_string($type) ? new Node\Identifier($type) : $type;
+        $this->type = $type;
     }
 
     public function getSubNodeNames(): array {
diff --git a/lib/PhpParser/Node/Stmt/ClassMethod.php b/lib/PhpParser/Node/Stmt/ClassMethod.php
index 3cadfd86..aa6424b6 100644
--- a/lib/PhpParser/Node/Stmt/ClassMethod.php
+++ b/lib/PhpParser/Node/Stmt/ClassMethod.php
@@ -51,7 +51,7 @@ class ClassMethod extends Node\Stmt implements FunctionLike {
      *     flags?: int,
      *     byRef?: bool,
      *     params?: Node\Param[],
-     *     returnType?: null|string|Node\Identifier|Node\Name|Node\ComplexType,
+     *     returnType?: null|Node\Identifier|Node\Name|Node\ComplexType,
      *     stmts?: Node\Stmt[]|null,
      *     attrGroups?: Node\AttributeGroup[],
      * } $subNodes Array of the following optional subnodes:
@@ -69,8 +69,7 @@ class ClassMethod extends Node\Stmt implements FunctionLike {
         $this->byRef = $subNodes['byRef'] ?? false;
         $this->name = \is_string($name) ? new Node\Identifier($name) : $name;
         $this->params = $subNodes['params'] ?? [];
-        $returnType = $subNodes['returnType'] ?? null;
-        $this->returnType = \is_string($returnType) ? new Node\Identifier($returnType) : $returnType;
+        $this->returnType = $subNodes['returnType'] ?? null;
         $this->stmts = array_key_exists('stmts', $subNodes) ? $subNodes['stmts'] : [];
         $this->attrGroups = $subNodes['attrGroups'] ?? [];
     }
diff --git a/lib/PhpParser/Node/Stmt/Function_.php b/lib/PhpParser/Node/Stmt/Function_.php
index 8948e211..feb5edfe 100644
--- a/lib/PhpParser/Node/Stmt/Function_.php
+++ b/lib/PhpParser/Node/Stmt/Function_.php
@@ -29,7 +29,7 @@ class Function_ extends Node\Stmt implements FunctionLike {
      * @param array{
      *     byRef?: bool,
      *     params?: Node\Param[],
-     *     returnType?: null|string|Node\Identifier|Node\Name|Node\ComplexType,
+     *     returnType?: null|Node\Identifier|Node\Name|Node\ComplexType,
      *     stmts?: Node\Stmt[],
      *     attrGroups?: Node\AttributeGroup[],
      * } $subNodes Array of the following optional subnodes:
@@ -45,8 +45,7 @@ class Function_ extends Node\Stmt implements FunctionLike {
         $this->byRef = $subNodes['byRef'] ?? false;
         $this->name = \is_string($name) ? new Node\Identifier($name) : $name;
         $this->params = $subNodes['params'] ?? [];
-        $returnType = $subNodes['returnType'] ?? null;
-        $this->returnType = \is_string($returnType) ? new Node\Identifier($returnType) : $returnType;
+        $this->returnType = $subNodes['returnType'] ?? null;
         $this->stmts = $subNodes['stmts'] ?? [];
         $this->attrGroups = $subNodes['attrGroups'] ?? [];
     }
diff --git a/lib/PhpParser/Node/Stmt/Property.php b/lib/PhpParser/Node/Stmt/Property.php
index 279207fd..5d668274 100644
--- a/lib/PhpParser/Node/Stmt/Property.php
+++ b/lib/PhpParser/Node/Stmt/Property.php
@@ -25,14 +25,14 @@ class Property extends Node\Stmt {
      * @param int                                     $flags      Modifiers
      * @param PropertyItem[]                      $props      Properties
      * @param array<string, mixed> $attributes Additional attributes
-     * @param null|string|Identifier|Name|ComplexType $type       Type declaration
+     * @param null|Identifier|Name|ComplexType $type Type declaration
      * @param Node\AttributeGroup[]                   $attrGroups PHP attribute groups
      */
-    public function __construct(int $flags, array $props, array $attributes = [], $type = null, array $attrGroups = []) {
+    public function __construct(int $flags, array $props, array $attributes = [], ?Node $type = null, array $attrGroups = []) {
         $this->attributes = $attributes;
         $this->flags = $flags;
         $this->props = $props;
-        $this->type = \is_string($type) ? new Identifier($type) : $type;
+        $this->type = $type;
         $this->attrGroups = $attrGroups;
     }
 
diff --git a/test/PhpParser/BuilderHelpersTest.php b/test/PhpParser/BuilderHelpersTest.php
index 493e71e9..d70be9d8 100644
--- a/test/PhpParser/BuilderHelpersTest.php
+++ b/test/PhpParser/BuilderHelpersTest.php
@@ -3,6 +3,7 @@
 namespace PhpParser;
 
 use PhpParser\Builder\Class_;
+use PhpParser\Node\Identifier;
 use PhpParser\Node\Scalar;
 use PhpParser\Node\Stmt;
 use PhpParser\Node\Expr;
@@ -136,7 +137,7 @@ class BuilderHelpersTest extends \PHPUnit\Framework\TestCase {
         $intName = new Node\Name('int');
         $this->assertSame($intName, BuilderHelpers::normalizeType($intName));
 
-        $intNullable = new Node\NullableType('int');
+        $intNullable = new Node\NullableType(new Identifier('int'));
         $this->assertSame($intNullable, BuilderHelpers::normalizeType($intNullable));
 
         $unionType = new Node\UnionType([new Node\Identifier('int'), new Node\Identifier('string')]);