diff --git a/src/Symfony/Component/CssSelector/CssSelectorConverter.php b/src/Symfony/Component/CssSelector/CssSelectorConverter.php
index 82064424e2..bbb6afe217 100644
--- a/src/Symfony/Component/CssSelector/CssSelectorConverter.php
+++ b/src/Symfony/Component/CssSelector/CssSelectorConverter.php
@@ -27,6 +27,10 @@ use Symfony\Component\CssSelector\XPath\Translator;
 class CssSelectorConverter
 {
     private $translator;
+    private $cache;
+
+    private static $xmlCache = [];
+    private static $htmlCache = [];
 
     /**
      * @param bool $html Whether HTML support should be enabled. Disable it for XML documents
@@ -37,6 +41,9 @@ class CssSelectorConverter
 
         if ($html) {
             $this->translator->registerExtension(new HtmlExtension($this->translator));
+            $this->cache = &self::$htmlCache;
+        } else {
+            $this->cache = &self::$xmlCache;
         }
 
         $this->translator
@@ -57,6 +64,6 @@ class CssSelectorConverter
      */
     public function toXPath(string $cssExpr, string $prefix = 'descendant-or-self::')
     {
-        return $this->translator->cssToXPath($cssExpr, $prefix);
+        return $this->cache[$prefix][$cssExpr] ?? $this->cache[$prefix][$cssExpr] = $this->translator->cssToXPath($cssExpr, $prefix);
     }
 }
diff --git a/src/Symfony/Component/CssSelector/Tests/CssSelectorConverterTest.php b/src/Symfony/Component/CssSelector/Tests/CssSelectorConverterTest.php
index 82e527c62e..420c33087d 100644
--- a/src/Symfony/Component/CssSelector/Tests/CssSelectorConverterTest.php
+++ b/src/Symfony/Component/CssSelector/Tests/CssSelectorConverterTest.php
@@ -26,6 +26,10 @@ class CssSelectorConverterTest extends TestCase
         $this->assertEquals("descendant-or-self::h1[@class and contains(concat(' ', normalize-space(@class), ' '), ' foo ')]", $converter->toXPath('h1.foo'));
         $this->assertEquals('descendant-or-self::foo:h1', $converter->toXPath('foo|h1'));
         $this->assertEquals('descendant-or-self::h1', $converter->toXPath('H1'));
+
+        // Test the cache layer
+        $converter = new CssSelectorConverter();
+        $this->assertEquals('descendant-or-self::h1', $converter->toXPath('H1'));
     }
 
     public function testCssToXPathXml()
@@ -33,6 +37,10 @@ class CssSelectorConverterTest extends TestCase
         $converter = new CssSelectorConverter(false);
 
         $this->assertEquals('descendant-or-self::H1', $converter->toXPath('H1'));
+
+        $converter = new CssSelectorConverter(false);
+        // Test the cache layer
+        $this->assertEquals('descendant-or-self::H1', $converter->toXPath('H1'));
     }
 
     public function testParseExceptions()
diff --git a/src/Symfony/Component/DomCrawler/CHANGELOG.md b/src/Symfony/Component/DomCrawler/CHANGELOG.md
index fa043cfd1e..b55e781f27 100644
--- a/src/Symfony/Component/DomCrawler/CHANGELOG.md
+++ b/src/Symfony/Component/DomCrawler/CHANGELOG.md
@@ -1,6 +1,11 @@
 CHANGELOG
 =========
 
+5.1.0
+-----
+
+* Added an internal cache layer on top of the CssSelectorConverter
+
 5.0.0
 -----