diff --git a/conf/config.neon b/conf/config.neon
index e0df3b916fd..f89fc6ebf7f 100644
--- a/conf/config.neon
+++ b/conf/config.neon
@@ -1438,6 +1438,9 @@ services:
 		tags:
 			- phpstan.typeSpecifier.functionTypeSpecifyingExtension
 
+	-
+		class: PHPStan\Type\Php\IsAFunctionTypeSpecifyingHelper
+
 	-
 		class: PHPStan\Type\Php\ArrayIsListFunctionTypeSpecifyingExtension
 		tags:
diff --git a/src/Type/Php/IsAFunctionTypeSpecifyingExtension.php b/src/Type/Php/IsAFunctionTypeSpecifyingExtension.php
index 490c8b7b5ae..1220eabab0e 100644
--- a/src/Type/Php/IsAFunctionTypeSpecifyingExtension.php
+++ b/src/Type/Php/IsAFunctionTypeSpecifyingExtension.php
@@ -9,18 +9,9 @@
 use PHPStan\Analyser\TypeSpecifierAwareExtension;
 use PHPStan\Analyser\TypeSpecifierContext;
 use PHPStan\Reflection\FunctionReflection;
-use PHPStan\Type\ClassStringType;
 use PHPStan\Type\Constant\ConstantBooleanType;
 use PHPStan\Type\Constant\ConstantStringType;
 use PHPStan\Type\FunctionTypeSpecifyingExtension;
-use PHPStan\Type\Generic\GenericClassStringType;
-use PHPStan\Type\IntersectionType;
-use PHPStan\Type\ObjectType;
-use PHPStan\Type\ObjectWithoutClassType;
-use PHPStan\Type\Type;
-use PHPStan\Type\TypeCombinator;
-use PHPStan\Type\TypeTraverser;
-use PHPStan\Type\UnionType;
 use function count;
 use function strtolower;
 
@@ -29,6 +20,12 @@ class IsAFunctionTypeSpecifyingExtension implements FunctionTypeSpecifyingExtens
 
 	private TypeSpecifier $typeSpecifier;
 
+	public function __construct(
+		private IsAFunctionTypeSpecifyingHelper $isAFunctionTypeSpecifyingHelper,
+	)
+	{
+	}
+
 	public function isFunctionSupported(FunctionReflection $functionReflection, FuncCall $node, TypeSpecifierContext $context): bool
 	{
 		return strtolower($functionReflection->getName()) === 'is_a'
@@ -48,40 +45,9 @@ public function specifyTypes(FunctionReflection $functionReflection, FuncCall $n
 			return new SpecifiedTypes([], []);
 		}
 
-		$type = TypeTraverser::map($classType, static function (Type $type, callable $traverse) use ($allowString): Type {
-			if ($type instanceof UnionType || $type instanceof IntersectionType) {
-				return $traverse($type);
-			}
-			if ($type instanceof ConstantStringType) {
-				if ($allowString) {
-					return TypeCombinator::union(
-						new ObjectType($type->getValue()),
-						new GenericClassStringType(new ObjectType($type->getValue())),
-					);
-				}
-				return new ObjectType($type->getValue());
-			}
-			if ($type instanceof GenericClassStringType) {
-				if ($allowString) {
-					return TypeCombinator::union(
-						$type->getGenericType(),
-						$type,
-					);
-				}
-				return $type->getGenericType();
-			}
-			if ($allowString) {
-				return TypeCombinator::union(
-					new ObjectWithoutClassType(),
-					new ClassStringType(),
-				);
-			}
-			return new ObjectWithoutClassType();
-		});
-
 		return $this->typeSpecifier->create(
 			$node->getArgs()[0]->value,
-			$type,
+			$this->isAFunctionTypeSpecifyingHelper->determineType($classType, $allowString),
 			$context,
 			false,
 			$scope,
diff --git a/src/Type/Php/IsAFunctionTypeSpecifyingHelper.php b/src/Type/Php/IsAFunctionTypeSpecifyingHelper.php
new file mode 100644
index 00000000000..8a689e60530
--- /dev/null
+++ b/src/Type/Php/IsAFunctionTypeSpecifyingHelper.php
@@ -0,0 +1,62 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Type\Php;
+
+use PHPStan\Type\ClassStringType;
+use PHPStan\Type\Constant\ConstantStringType;
+use PHPStan\Type\Generic\GenericClassStringType;
+use PHPStan\Type\IntersectionType;
+use PHPStan\Type\ObjectType;
+use PHPStan\Type\ObjectWithoutClassType;
+use PHPStan\Type\Type;
+use PHPStan\Type\TypeCombinator;
+use PHPStan\Type\TypeTraverser;
+use PHPStan\Type\UnionType;
+
+final class IsAFunctionTypeSpecifyingHelper
+{
+
+	public function determineType(
+		Type $classType,
+		bool $allowString,
+	): Type
+	{
+		return TypeTraverser::map(
+			$classType,
+			static function (Type $type, callable $traverse) use ($allowString): Type {
+				if ($type instanceof UnionType || $type instanceof IntersectionType) {
+					return $traverse($type);
+				}
+				if ($type instanceof ConstantStringType) {
+					if ($allowString) {
+						return TypeCombinator::union(
+							new ObjectType($type->getValue()),
+							new GenericClassStringType(new ObjectType($type->getValue())),
+						);
+					}
+
+					return new ObjectType($type->getValue());
+				}
+				if ($type instanceof GenericClassStringType) {
+					if ($allowString) {
+						return TypeCombinator::union(
+							$type->getGenericType(),
+							$type,
+						);
+					}
+
+					return $type->getGenericType();
+				}
+				if ($allowString) {
+					return TypeCombinator::union(
+						new ObjectWithoutClassType(),
+						new ClassStringType(),
+					);
+				}
+
+				return new ObjectWithoutClassType();
+			},
+		);
+	}
+
+}
diff --git a/src/Type/Php/IsSubclassOfFunctionTypeSpecifyingExtension.php b/src/Type/Php/IsSubclassOfFunctionTypeSpecifyingExtension.php
index c4633421943..15c773784ee 100644
--- a/src/Type/Php/IsSubclassOfFunctionTypeSpecifyingExtension.php
+++ b/src/Type/Php/IsSubclassOfFunctionTypeSpecifyingExtension.php
@@ -9,18 +9,9 @@
 use PHPStan\Analyser\TypeSpecifierAwareExtension;
 use PHPStan\Analyser\TypeSpecifierContext;
 use PHPStan\Reflection\FunctionReflection;
-use PHPStan\Type\ClassStringType;
 use PHPStan\Type\Constant\ConstantBooleanType;
 use PHPStan\Type\Constant\ConstantStringType;
 use PHPStan\Type\FunctionTypeSpecifyingExtension;
-use PHPStan\Type\Generic\GenericClassStringType;
-use PHPStan\Type\IntersectionType;
-use PHPStan\Type\ObjectType;
-use PHPStan\Type\ObjectWithoutClassType;
-use PHPStan\Type\Type;
-use PHPStan\Type\TypeCombinator;
-use PHPStan\Type\TypeTraverser;
-use PHPStan\Type\UnionType;
 use function count;
 use function strtolower;
 
@@ -29,6 +20,12 @@ class IsSubclassOfFunctionTypeSpecifyingExtension implements FunctionTypeSpecify
 
 	private TypeSpecifier $typeSpecifier;
 
+	public function __construct(
+		private IsAFunctionTypeSpecifyingHelper $isAFunctionTypeSpecifyingHelper,
+	)
+	{
+	}
+
 	public function isFunctionSupported(FunctionReflection $functionReflection, FuncCall $node, TypeSpecifierContext $context): bool
 	{
 		return strtolower($functionReflection->getName()) === 'is_subclass_of'
@@ -48,40 +45,9 @@ public function specifyTypes(FunctionReflection $functionReflection, FuncCall $n
 			return new SpecifiedTypes([], []);
 		}
 
-		$type = TypeTraverser::map($classType, static function (Type $type, callable $traverse) use ($allowString): Type {
-			if ($type instanceof UnionType || $type instanceof IntersectionType) {
-				return $traverse($type);
-			}
-			if ($type instanceof ConstantStringType) {
-				if ($allowString) {
-					return TypeCombinator::union(
-						new ObjectType($type->getValue()),
-						new GenericClassStringType(new ObjectType($type->getValue())),
-					);
-				}
-				return new ObjectType($type->getValue());
-			}
-			if ($type instanceof GenericClassStringType) {
-				if ($allowString) {
-					return TypeCombinator::union(
-						$type->getGenericType(),
-						$type,
-					);
-				}
-				return $type->getGenericType();
-			}
-			if ($allowString) {
-				return TypeCombinator::union(
-					new ObjectWithoutClassType(),
-					new ClassStringType(),
-				);
-			}
-			return new ObjectWithoutClassType();
-		});
-
 		return $this->typeSpecifier->create(
 			$node->getArgs()[0]->value,
-			$type,
+			$this->isAFunctionTypeSpecifyingHelper->determineType($classType, $allowString),
 			$context,
 			false,
 			$scope,