diff --git a/src/Symfony/Component/Form/ButtonBuilder.php b/src/Symfony/Component/Form/ButtonBuilder.php
index 46ca01c6d435b..a04b019af1127 100644
--- a/src/Symfony/Component/Form/ButtonBuilder.php
+++ b/src/Symfony/Component/Form/ButtonBuilder.php
@@ -61,17 +61,7 @@ public function __construct(?string $name, array $options = [])
         $this->name = $name;
         $this->options = $options;
 
-        if (\preg_match('/^([^a-z0-9_].*)?(.*[^a-zA-Z0-9_\-:].*)?$/D', $name, $matches)) {
-            if (isset($matches[1])) {
-                @trigger_error(sprintf('Using names for buttons that do not start with a letter, a digit, or an underscore is deprecated since Symfony 4.3 and will throw an exception in 5.0 ("%s" given).', $name), E_USER_DEPRECATED);
-            }
-            if (isset($matches[2])) {
-                @trigger_error(sprintf('Using names for buttons that do not contain only letters, digits, underscores ("_"), hyphens ("-") and colons (":") ("%s" given) is deprecated since Symfony 4.3 and will throw an exception in 5.0.', $name), E_USER_DEPRECATED);
-            }
-        }
-
-        // to be added in 5.0
-        // FormConfigBuilder::validateName($name);
+        FormConfigBuilder::validateName($name);
     }
 
     /**
diff --git a/src/Symfony/Component/Form/CHANGELOG.md b/src/Symfony/Component/Form/CHANGELOG.md
index 65cec5df04e03..3a0e9bba8d4c9 100644
--- a/src/Symfony/Component/Form/CHANGELOG.md
+++ b/src/Symfony/Component/Form/CHANGELOG.md
@@ -4,6 +4,8 @@ CHANGELOG
 5.0.0
 -----
 
+ * Using names for buttons that do not start with a letter, a digit, or an underscore throw an exception
+ * Using names for buttons that do not contain only letters, digits, underscores, hyphens, and colons throw an exception.
  * removed the `ChoiceLoaderInterface` implementation in `CountryType`, `LanguageType`, `LocaleType` and `CurrencyType`
 
 4.3.0
diff --git a/src/Symfony/Component/Form/Tests/ButtonBuilderTest.php b/src/Symfony/Component/Form/Tests/ButtonBuilderTest.php
index e987ef7eabf20..126e550b312f5 100644
--- a/src/Symfony/Component/Form/Tests/ButtonBuilderTest.php
+++ b/src/Symfony/Component/Form/Tests/ButtonBuilderTest.php
@@ -40,7 +40,8 @@ public function testValidNames($name)
     }
 
     /**
-     * @group legacy
+     * @expectedException \Symfony\Component\Form\Exception\InvalidArgumentException
+     * @expectedExceptionMessage The name "button[]" contains illegal characters. Names should start with a letter, digit or underscore and only contain letters, digits, numbers, underscores ("_"), hyphens ("-") and colons (":").
      */
     public function testNameContainingIllegalCharacters()
     {