diff --git a/src/Cache/KeySanitizerCache.php b/src/Cache/KeySanitizerCache.php
index 0d3785c6..0f78ca25 100644
--- a/src/Cache/KeySanitizerCache.php
+++ b/src/Cache/KeySanitizerCache.php
@@ -4,12 +4,12 @@
 
 namespace CuyZ\Valinor\Cache;
 
-use Closure;
 use CuyZ\Valinor\Utility\Package;
 use Psr\SimpleCache\CacheInterface;
 use Traversable;
 
 use function hash;
+use function strstr;
 
 /**
  * @internal
@@ -21,21 +21,28 @@ final class KeySanitizerCache implements WarmupCache
 {
     private static string $version;
 
-    /** @var Closure(string): string */
-    private Closure $sanitize;
-
     public function __construct(
         /** @var CacheInterface<EntryType> */
         private CacheInterface $delegate
-    ) {
-        // Two things:
-        // 1. We append the current version of the package to the cache key in
-        //    order to avoid collisions between entries from different versions
-        //    of the library.
-        // 2. The key is hashed so that it does not contain illegal characters.
-        //    @see https://www.php-fig.org/psr/psr-16/#12-definitions
-        // @infection-ignore-all
-        $this->sanitize = static fn (string $key) => $key . hash('sha1', self::$version ??= PHP_VERSION . '/' . Package::version());
+    ) {}
+
+    /**
+     * Two things:
+     * 1. We append the current version of the package to the cache key in order
+     *    to avoid collisions between entries from different versions of the
+     *    library.
+     * 2. The key is hashed so that it does not contain illegal characters.
+     *    @see https://www.php-fig.org/psr/psr-16/#12-definitions
+     *
+     * @infection-ignore-all
+     */
+    private function sanitize(string $key): string
+    {
+        self::$version ??= PHP_VERSION . '/' . Package::version();
+
+        $firstPart = strstr($key, "\0", before_needle: true);
+
+        return $firstPart . hash('xxh128', $key . self::$version);
     }
 
     public function warmup(): void
@@ -47,17 +54,17 @@ public function warmup(): void
 
     public function get($key, $default = null): mixed
     {
-        return $this->delegate->get(($this->sanitize)($key), $default);
+        return $this->delegate->get($this->sanitize($key), $default);
     }
 
     public function set($key, $value, $ttl = null): bool
     {
-        return $this->delegate->set(($this->sanitize)($key), $value, $ttl);
+        return $this->delegate->set($this->sanitize($key), $value, $ttl);
     }
 
     public function delete($key): bool
     {
-        return $this->delegate->delete(($this->sanitize)($key));
+        return $this->delegate->delete($this->sanitize($key));
     }
 
     public function clear(): bool
@@ -67,7 +74,7 @@ public function clear(): bool
 
     public function has($key): bool
     {
-        return $this->delegate->has(($this->sanitize)($key));
+        return $this->delegate->has($this->sanitize($key));
     }
 
     /**
@@ -76,7 +83,7 @@ public function has($key): bool
     public function getMultiple($keys, $default = null): Traversable
     {
         foreach ($keys as $key) {
-            yield $key => $this->delegate->get(($this->sanitize)($key), $default);
+            yield $key => $this->delegate->get($this->sanitize($key), $default);
         }
     }
 
@@ -85,7 +92,7 @@ public function setMultiple($values, $ttl = null): bool
         $versionedValues = [];
 
         foreach ($values as $key => $value) {
-            $versionedValues[($this->sanitize)($key)] = $value;
+            $versionedValues[$this->sanitize($key)] = $value;
         }
 
         return $this->delegate->setMultiple($versionedValues, $ttl);
@@ -96,7 +103,7 @@ public function deleteMultiple($keys): bool
         $transformedKeys = [];
 
         foreach ($keys as $key) {
-            $transformedKeys[] = ($this->sanitize)($key);
+            $transformedKeys[] = $this->sanitize($key);
         }
 
         return $this->delegate->deleteMultiple($transformedKeys);
diff --git a/src/Definition/Repository/Cache/CacheClassDefinitionRepository.php b/src/Definition/Repository/Cache/CacheClassDefinitionRepository.php
index c0992bad..89a720e4 100644
--- a/src/Definition/Repository/Cache/CacheClassDefinitionRepository.php
+++ b/src/Definition/Repository/Cache/CacheClassDefinitionRepository.php
@@ -9,8 +9,6 @@
 use CuyZ\Valinor\Type\ObjectType;
 use Psr\SimpleCache\CacheInterface;
 
-use function hash;
-
 /** @internal */
 final class CacheClassDefinitionRepository implements ClassDefinitionRepository
 {
@@ -23,7 +21,7 @@ public function __construct(
     public function for(ObjectType $type): ClassDefinition
     {
         // @infection-ignore-all
-        $key = 'class-definition' . hash('sha1', $type->toString());
+        $key = "class-definition-\0" . $type->toString();
 
         $entry = $this->cache->get($key);
 
diff --git a/src/Definition/Repository/Cache/CacheFunctionDefinitionRepository.php b/src/Definition/Repository/Cache/CacheFunctionDefinitionRepository.php
index b56b729b..265b8189 100644
--- a/src/Definition/Repository/Cache/CacheFunctionDefinitionRepository.php
+++ b/src/Definition/Repository/Cache/CacheFunctionDefinitionRepository.php
@@ -9,8 +9,6 @@
 use CuyZ\Valinor\Utility\Reflection\Reflection;
 use Psr\SimpleCache\CacheInterface;
 
-use function hash;
-
 /** @internal */
 final class CacheFunctionDefinitionRepository implements FunctionDefinitionRepository
 {
@@ -25,7 +23,7 @@ public function for(callable $function): FunctionDefinition
         $reflection = Reflection::function($function);
 
         // @infection-ignore-all
-        $key = 'function-definition-' . hash('sha1', $reflection->getFileName() . $reflection->getStartLine() . $reflection->getEndLine());
+        $key = "function-definition-\0" . $reflection->getFileName() . ':' . $reflection->getStartLine() . '-' . $reflection->getEndLine();
 
         $entry = $this->cache->get($key);