diff --git a/src/Symfony/Component/Form/Extension/Core/DataTransformer/DateTimeToLocalizedStringTransformer.php b/src/Symfony/Component/Form/Extension/Core/DataTransformer/DateTimeToLocalizedStringTransformer.php
index 4d7eed8b0c..8d73404b5d 100644
--- a/src/Symfony/Component/Form/Extension/Core/DataTransformer/DateTimeToLocalizedStringTransformer.php
+++ b/src/Symfony/Component/Form/Extension/Core/DataTransformer/DateTimeToLocalizedStringTransformer.php
@@ -172,7 +172,7 @@ class DateTimeToLocalizedStringTransformer extends BaseDateTimeTransformer
         $calendar = $this->calendar;
         $pattern = $this->pattern;
 
-        $intlDateFormatter = new \IntlDateFormatter(\Locale::getDefault(), $dateFormat, $timeFormat, $timezone, $calendar, $pattern);
+        $intlDateFormatter = new \IntlDateFormatter(\Locale::getDefault(), $dateFormat, $timeFormat, $timezone, $calendar, $pattern ?? '');
 
         // new \intlDateFormatter may return null instead of false in case of failure, see https://bugs.php.net/66323
         if (!$intlDateFormatter) {
diff --git a/src/Symfony/Component/Form/Extension/Core/Type/DateType.php b/src/Symfony/Component/Form/Extension/Core/Type/DateType.php
index e446151d2a..0a20d94e66 100644
--- a/src/Symfony/Component/Form/Extension/Core/Type/DateType.php
+++ b/src/Symfony/Component/Form/Extension/Core/Type/DateType.php
@@ -51,14 +51,14 @@ class DateType extends AbstractType
         $dateFormat = \is_int($options['format']) ? $options['format'] : self::DEFAULT_FORMAT;
         $timeFormat = \IntlDateFormatter::NONE;
         $calendar = \IntlDateFormatter::GREGORIAN;
-        $pattern = \is_string($options['format']) ? $options['format'] : null;
+        $pattern = \is_string($options['format']) ? $options['format'] : '';
 
         if (!\in_array($dateFormat, self::$acceptedFormats, true)) {
             throw new InvalidOptionsException('The "format" option must be one of the IntlDateFormatter constants (FULL, LONG, MEDIUM, SHORT) or a string representing a custom format.');
         }
 
         if ('single_text' === $options['widget']) {
-            if (null !== $pattern && false === strpos($pattern, 'y') && false === strpos($pattern, 'M') && false === strpos($pattern, 'd')) {
+            if ('' !== $pattern && false === strpos($pattern, 'y') && false === strpos($pattern, 'M') && false === strpos($pattern, 'd')) {
                 throw new InvalidOptionsException(sprintf('The "format" option should contain the letters "y", "M" or "d". Its current value is "%s".', $pattern));
             }
 
@@ -71,7 +71,7 @@ class DateType extends AbstractType
                 $pattern
             ));
         } else {
-            if (null !== $pattern && (false === strpos($pattern, 'y') || false === strpos($pattern, 'M') || false === strpos($pattern, 'd'))) {
+            if ('' !== $pattern && (false === strpos($pattern, 'y') || false === strpos($pattern, 'M') || false === strpos($pattern, 'd'))) {
                 throw new InvalidOptionsException(sprintf('The "format" option should contain the letters "y", "M" and "d". Its current value is "%s".', $pattern));
             }
 
diff --git a/src/Symfony/Component/Intl/DateFormatter/IntlDateFormatter.php b/src/Symfony/Component/Intl/DateFormatter/IntlDateFormatter.php
index d77c094117..317510c236 100644
--- a/src/Symfony/Component/Intl/DateFormatter/IntlDateFormatter.php
+++ b/src/Symfony/Component/Intl/DateFormatter/IntlDateFormatter.php
@@ -145,6 +145,10 @@ abstract class IntlDateFormatter
         $this->datetype = null !== $datetype ? $datetype : self::FULL;
         $this->timetype = null !== $timetype ? $timetype : self::FULL;
 
+        if ('' === ($pattern ?? '')) {
+            $pattern = $this->getDefaultPattern();
+        }
+
         $this->setPattern($pattern);
         $this->setTimeZone($timezone);
     }
@@ -485,7 +489,7 @@ abstract class IntlDateFormatter
     /**
      * Set the formatter's pattern.
      *
-     * @param string|null $pattern A pattern string in conformance with the ICU IntlDateFormatter documentation
+     * @param string $pattern A pattern string in conformance with the ICU IntlDateFormatter documentation
      *
      * @return bool true on success or false on failure
      *
@@ -494,11 +498,7 @@ abstract class IntlDateFormatter
      */
     public function setPattern($pattern)
     {
-        if (null === $pattern) {
-            $pattern = $this->getDefaultPattern();
-        }
-
-        $this->pattern = $pattern;
+        $this->pattern = (string) $pattern;
 
         return true;
     }