diff --git a/src/Cache/Cache.php b/src/Cache/Cache.php
index 83472f05de..3e9b97cf3b 100644
--- a/src/Cache/Cache.php
+++ b/src/Cache/Cache.php
@@ -17,19 +17,20 @@ public function __construct(CacheStorage $storage)
 	 * @param string $key
 	 * @return mixed|null
 	 */
-	public function load(string $key)
+	public function load(string $key, string $variableKey)
 	{
-		return $this->storage->load($key);
+		return $this->storage->load($key, $variableKey);
 	}
 
 	/**
 	 * @param string $key
+	 * @param string $variableKey
 	 * @param mixed $data
 	 * @return void
 	 */
-	public function save(string $key, $data): void
+	public function save(string $key, string $variableKey, $data): void
 	{
-		$this->storage->save($key, $data);
+		$this->storage->save($key, $variableKey, $data);
 	}
 
 }
diff --git a/src/Cache/CacheItem.php b/src/Cache/CacheItem.php
new file mode 100644
index 0000000000..10e1ccb0a2
--- /dev/null
+++ b/src/Cache/CacheItem.php
@@ -0,0 +1,46 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Cache;
+
+class CacheItem
+{
+
+	/** @var string */
+	private $variableKey;
+
+	/** @var mixed */
+	private $data;
+
+	/**
+	 * @param string $variableKey
+	 * @param mixed $data
+	 */
+	public function __construct(string $variableKey, $data)
+	{
+		$this->variableKey = $variableKey;
+		$this->data = $data;
+	}
+
+	public function isVariableKeyValid(string $variableKey): bool
+	{
+		return $this->variableKey === $variableKey;
+	}
+
+	/**
+	 * @return mixed
+	 */
+	public function getData()
+	{
+		return $this->data;
+	}
+
+	/**
+	 * @param mixed[] $properties
+	 * @return self
+	 */
+	public static function __set_state(array $properties): self
+	{
+		return new self($properties['variableKey'], $properties['data']);
+	}
+
+}
diff --git a/src/Cache/CacheStorage.php b/src/Cache/CacheStorage.php
index e63091b5fc..a9227b0eca 100644
--- a/src/Cache/CacheStorage.php
+++ b/src/Cache/CacheStorage.php
@@ -7,15 +7,17 @@ interface CacheStorage
 
 	/**
 	 * @param string $key
+	 * @param string $variableKey
 	 * @return mixed|null
 	 */
-	public function load(string $key);
+	public function load(string $key, string $variableKey);
 
 	/**
 	 * @param string $key
+	 * @param string $variableKey
 	 * @param mixed $data
 	 * @return void
 	 */
-	public function save(string $key, $data): void;
+	public function save(string $key, string $variableKey, $data): void;
 
 }
diff --git a/src/Cache/FileCacheStorage.php b/src/Cache/FileCacheStorage.php
index df7b8f6380..2593d1e213 100644
--- a/src/Cache/FileCacheStorage.php
+++ b/src/Cache/FileCacheStorage.php
@@ -23,22 +23,36 @@ private function makeDir(string $directory): void
 
 	/**
 	 * @param string $key
+	 * @param string $variableKey
 	 * @return mixed|null
 	 */
-	public function load(string $key)
+	public function load(string $key, string $variableKey)
 	{
-		return (function (string $key) {
+		return (function (string $key, string $variableKey) {
 			$filePath = $this->getFilePath($key);
-			return is_file($filePath) ? require $filePath : null;
-		})($key);
+			if (!is_file($filePath)) {
+				return null;
+			}
+
+			$cacheItem = require $filePath;
+			if (!$cacheItem instanceof CacheItem) {
+				return null;
+			}
+			if (!$cacheItem->isVariableKeyValid($variableKey)) {
+				return null;
+			}
+
+			return $cacheItem->getData();
+		})($key, $variableKey);
 	}
 
 	/**
 	 * @param string $key
+	 * @param string $variableKey
 	 * @param mixed $data
 	 * @return void
 	 */
-	public function save(string $key, $data): void
+	public function save(string $key, string $variableKey, $data): void
 	{
 		$path = $this->getFilePath($key);
 		$this->makeDir(dirname($path));
@@ -46,7 +60,7 @@ public function save(string $key, $data): void
 			$path,
 			sprintf(
 				"<?php declare(strict_types = 1);\n\nreturn %s;",
-				var_export($data, true)
+				var_export(new CacheItem($variableKey, $data), true)
 			)
 		);
 		if ($success === false) {
diff --git a/src/Cache/MemoryCacheStorage.php b/src/Cache/MemoryCacheStorage.php
index 3ae63aaefb..575d9ff633 100644
--- a/src/Cache/MemoryCacheStorage.php
+++ b/src/Cache/MemoryCacheStorage.php
@@ -5,26 +5,37 @@
 class MemoryCacheStorage implements CacheStorage
 {
 
-	/** @var mixed[] */
+	/** @var array<string, \PHPStan\Cache\CacheItem> */
 	private $storage = [];
 
 	/**
 	 * @param string $key
+	 * @param string $variableKey
 	 * @return mixed|null
 	 */
-	public function load(string $key)
+	public function load(string $key, string $variableKey)
 	{
-		return $this->storage[$key] ?? null;
+		if (!isset($this->storage[$key])) {
+			return null;
+		}
+
+		$item = $this->storage[$key];
+		if (!$item->isVariableKeyValid($variableKey)) {
+			return null;
+		}
+
+		return $item->getData();
 	}
 
 	/**
 	 * @param string $key
+	 * @param string $variableKey
 	 * @param mixed $data
 	 * @return void
 	 */
-	public function save(string $key, $data): void
+	public function save(string $key, string $variableKey, $data): void
 	{
-		$this->storage[$key] = $data;
+		$this->storage[$key] = new CacheItem($variableKey, $data);
 	}
 
 }
diff --git a/src/Reflection/Php/PhpFunctionReflection.php b/src/Reflection/Php/PhpFunctionReflection.php
index f07f472d66..42c31d3b96 100644
--- a/src/Reflection/Php/PhpFunctionReflection.php
+++ b/src/Reflection/Php/PhpFunctionReflection.php
@@ -171,12 +171,13 @@ private function isVariadic(): bool
 			if ($modifiedTime === false) {
 				$modifiedTime = time();
 			}
-			$key = sprintf('variadic-function-%s-%s-%d-v1', $functionName, $fileName, $modifiedTime);
-			$cachedResult = $this->cache->load($key);
+			$variableCacheKey = sprintf('%d-v1', $modifiedTime);
+			$key = sprintf('variadic-function-%s-%s', $functionName, $fileName);
+			$cachedResult = $this->cache->load($key, $variableCacheKey);
 			if ($cachedResult === null) {
 				$nodes = $this->parser->parseFile($fileName);
 				$result = $this->callsFuncGetArgs($nodes);
-				$this->cache->save($key, $result);
+				$this->cache->save($key, $variableCacheKey, $result);
 				return $result;
 			}
 
diff --git a/src/Reflection/Php/PhpMethodReflection.php b/src/Reflection/Php/PhpMethodReflection.php
index 9a55bb7afa..48da1a8f06 100644
--- a/src/Reflection/Php/PhpMethodReflection.php
+++ b/src/Reflection/Php/PhpMethodReflection.php
@@ -281,12 +281,13 @@ private function isVariadic(): bool
 			if ($modifiedTime === false) {
 				$modifiedTime = time();
 			}
-			$key = sprintf('variadic-method-%s-%s-%s-%d-v2', $declaringClass->getName(), $this->reflection->getName(), $filename, $modifiedTime);
-			$cachedResult = $this->cache->load($key);
+			$key = sprintf('variadic-method-%s-%s-%s', $declaringClass->getName(), $this->reflection->getName(), $filename);
+			$variableCacheKey = sprintf('%d-v2', $modifiedTime);
+			$cachedResult = $this->cache->load($key, $variableCacheKey);
 			if ($cachedResult === null || !is_bool($cachedResult)) {
 				$nodes = $this->parser->parseFile($filename);
 				$result = $this->callsFuncGetArgs($declaringClass, $nodes);
-				$this->cache->save($key, $result);
+				$this->cache->save($key, $variableCacheKey, $result);
 				return $result;
 			}
 
diff --git a/src/Type/FileTypeMapper.php b/src/Type/FileTypeMapper.php
index 589848d65e..09816ce3dc 100644
--- a/src/Type/FileTypeMapper.php
+++ b/src/Type/FileTypeMapper.php
@@ -152,15 +152,15 @@ private function resolvePhpDocStringToDocNode(string $phpDocString): PhpDocNode
 		} catch (\OutOfBoundsException $e) {
 			// skip
 		}
-		$cacheKey = sprintf('phpdocstring-%s-%s', $phpDocString, $phpDocParserVersion);
-		$phpDocNodeSerializedString = $this->cache->load($cacheKey);
+		$cacheKey = sprintf('phpdocstring-%s', $phpDocString);
+		$phpDocNodeSerializedString = $this->cache->load($cacheKey, $phpDocParserVersion);
 		if ($phpDocNodeSerializedString !== null) {
 			return unserialize($phpDocNodeSerializedString);
 		}
 
 		$phpDocNode = $this->phpDocStringResolver->resolve($phpDocString);
 		if ($this->shouldPhpDocNodeBeCachedToDisk($phpDocNode)) {
-			$this->cache->save($cacheKey, serialize($phpDocNode));
+			$this->cache->save($cacheKey, $phpDocParserVersion, serialize($phpDocNode));
 		}
 
 		return $phpDocNode;
@@ -190,12 +190,13 @@ private function getResolvedPhpDocMap(string $fileName): array
 			if ($modifiedTime === false) {
 				$modifiedTime = time();
 			}
-			$cacheKey = sprintf('%s-phpdocstring-%d', $fileName, $modifiedTime);
-			$map = $this->cache->load($cacheKey);
+			$cacheKey = sprintf('%s-phpdocstring', $fileName);
+			$modifiedTimeString = sprintf('%d', $modifiedTime);
+			$map = $this->cache->load($cacheKey, $modifiedTimeString);
 
 			if ($map === null) {
 				$map = $this->createResolvedPhpDocMap($fileName);
-				$this->cache->save($cacheKey, $map);
+				$this->cache->save($cacheKey, $modifiedTimeString, $map);
 			}
 
 			$this->memoryCache[$fileName] = $map;