diff --git a/src/Analyser/ExprHandler/Helper/EarlyTerminatingCallHelper.php b/src/Analyser/ExprHandler/Helper/EarlyTerminatingCallHelper.php
index d44df0587f..04ea31fe51 100644
--- a/src/Analyser/ExprHandler/Helper/EarlyTerminatingCallHelper.php
+++ b/src/Analyser/ExprHandler/Helper/EarlyTerminatingCallHelper.php
@@ -5,9 +5,9 @@
 use PHPStan\DependencyInjection\AutowiredParameter;
 use PHPStan\DependencyInjection\AutowiredService;
 use PHPStan\Reflection\ReflectionProvider;
+use PHPStan\Type\ExtensionClassHelper;
 use PHPStan\Type\Type;
 use function array_key_exists;
-use function array_merge;
 use function in_array;
 use function strtolower;
 
@@ -57,8 +57,8 @@ public function isEarlyTerminatingMethodCall(string $methodName, Type $calledOnT
 				continue;
 			}
 
-			$classReflection = $this->reflectionProvider->getClass($referencedClass);
-			foreach (array_merge([$referencedClass], $classReflection->getParentClassesNames(), $classReflection->getNativeReflection()->getInterfaceNames()) as $className) {
+			$extensionClassNames = ExtensionClassHelper::getExtensionClassNames($this->reflectionProvider, $referencedClass);
+			foreach ($extensionClassNames as $className) {
 				if (!isset($this->earlyTerminatingMethodCalls[$className])) {
 					continue;
 				}
diff --git a/src/Analyser/TypeSpecifier.php b/src/Analyser/TypeSpecifier.php
index 3bc9039336..d2da6b934b 100644
--- a/src/Analyser/TypeSpecifier.php
+++ b/src/Analyser/TypeSpecifier.php
@@ -27,6 +27,7 @@
 use PHPStan\Type\ConditionalTypeForParameter;
 use PHPStan\Type\Constant\ConstantBooleanType;
 use PHPStan\Type\Constant\ConstantIntegerType;
+use PHPStan\Type\ExtensionClassHelper;
 use PHPStan\Type\FunctionTypeSpecifyingExtension;
 use PHPStan\Type\Generic\TemplateType;
 use PHPStan\Type\IntegerRangeType;
@@ -791,8 +792,8 @@ public function getStaticMethodTypeSpecifyingExtensionsForClass(string $classNam
 	private function getTypeSpecifyingExtensionsForType(array $extensions, string $className): array
 	{
 		$extensionsForClass = [[]];
-		$class = $this->reflectionProvider->getClass($className);
-		foreach (array_merge([$className], $class->getParentClassesNames(), $class->getNativeReflection()->getInterfaceNames()) as $extensionClassName) {
+		$extensionClassNames = ExtensionClassHelper::getExtensionClassNames($this->reflectionProvider, $className);
+		foreach ($extensionClassNames as $extensionClassName) {
 			if (!isset($extensions[$extensionClassName])) {
 				continue;
 			}
diff --git a/src/Type/DynamicReturnTypeExtensionRegistry.php b/src/Type/DynamicReturnTypeExtensionRegistry.php
index 5002627ec5..4f9862a5b3 100644
--- a/src/Type/DynamicReturnTypeExtensionRegistry.php
+++ b/src/Type/DynamicReturnTypeExtensionRegistry.php
@@ -83,8 +83,8 @@ private function getDynamicExtensionsForType(array $extensions, string $classNam
 		}
 
 		$extensionsForClass = [[]];
-		$class = $this->reflectionProvider->getClass($className);
-		foreach (array_merge([$className], $class->getParentClassesNames(), $class->getNativeReflection()->getInterfaceNames()) as $extensionClassName) {
+		$extensionClassNames = ExtensionClassHelper::getExtensionClassNames($this->reflectionProvider, $className);
+		foreach ($extensionClassNames as $extensionClassName) {
 			$extensionClassName = strtolower($extensionClassName);
 			if (!isset($extensions[$extensionClassName])) {
 				continue;
diff --git a/src/Type/ExtensionClassHelper.php b/src/Type/ExtensionClassHelper.php
new file mode 100644
index 0000000000..21c6f610e8
--- /dev/null
+++ b/src/Type/ExtensionClassHelper.php
@@ -0,0 +1,28 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Type;
+
+use PHPStan\Reflection\ReflectionProvider;
+use function array_key_exists;
+use function array_merge;
+
+final class ExtensionClassHelper
+{
+
+	/** @var array<string, array<string>> */
+	private static array $extensionClassNames = [];
+
+	/**
+	 * @return string[]
+	 */
+	public static function getExtensionClassNames(ReflectionProvider $reflectionProvider, string $className): array
+	{
+		if (!array_key_exists($className, self::$extensionClassNames)) {
+			$class = $reflectionProvider->getClass($className);
+			self::$extensionClassNames[$className] = array_merge([$className], $class->getParentClassesNames(), $class->getNativeReflection()->getInterfaceNames());
+		}
+
+		return self::$extensionClassNames[$className];
+	}
+
+}