diff --git a/.github/workflows/intl-data-tests.yml b/.github/workflows/intl-data-tests.yml
index 0925858432..0ca0322281 100644
--- a/.github/workflows/intl-data-tests.yml
+++ b/.github/workflows/intl-data-tests.yml
@@ -15,7 +15,7 @@ defaults:
 jobs:
   tests:
     name: Tests (intl-data)
-    runs-on: ubuntu-latest
+    runs-on: Ubuntu-20.04
 
     steps:
       - name: Checkout
diff --git a/.github/workflows/phpunit-bridge.yml b/.github/workflows/phpunit-bridge.yml
index 8fa97980ff..b503ce48d8 100644
--- a/.github/workflows/phpunit-bridge.yml
+++ b/.github/workflows/phpunit-bridge.yml
@@ -15,7 +15,7 @@ defaults:
 jobs:
   lint:
     name: Lint
-    runs-on: ubuntu-latest
+    runs-on: Ubuntu-20.04
 
     steps:
       - name: Checkout
diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index bdcb488e63..d8e6586e5b 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -11,7 +11,7 @@ defaults:
 jobs:
   integration:
     name: Integration
-    runs-on: ubuntu-latest
+    runs-on: Ubuntu-20.04
 
     strategy:
       matrix:
diff --git a/src/Symfony/Component/Serializer/Normalizer/DateIntervalNormalizer.php b/src/Symfony/Component/Serializer/Normalizer/DateIntervalNormalizer.php
index a47fd76b45..7a02d18276 100644
--- a/src/Symfony/Component/Serializer/Normalizer/DateIntervalNormalizer.php
+++ b/src/Symfony/Component/Serializer/Normalizer/DateIntervalNormalizer.php
@@ -96,7 +96,7 @@ class DateIntervalNormalizer implements NormalizerInterface, DenormalizerInterfa
                 $dateIntervalFormat = substr($dateIntervalFormat, 2);
                 break;
         }
-        $valuePattern = '/^'.$signPattern.preg_replace('/%([yYmMdDhHiIsSwW])(\w)/', '(?P<$1>\d+)$2', $dateIntervalFormat).'$/';
+        $valuePattern = '/^'.$signPattern.preg_replace('/%([yYmMdDhHiIsSwW])(\w)/', '(?:(?P<$1>\d+)$2)?', preg_replace('/(T.*)$/', '($1)?', $dateIntervalFormat)).'$/';
         if (!preg_match($valuePattern, $data)) {
             throw new UnexpectedValueException(sprintf('Value "%s" contains intervals not accepted by format "%s".', $data, $dateIntervalFormat));
         }
diff --git a/src/Symfony/Component/Serializer/Tests/Normalizer/DateIntervalNormalizerTest.php b/src/Symfony/Component/Serializer/Tests/Normalizer/DateIntervalNormalizerTest.php
index df87fa7df6..e45a6b042f 100644
--- a/src/Symfony/Component/Serializer/Tests/Normalizer/DateIntervalNormalizerTest.php
+++ b/src/Symfony/Component/Serializer/Tests/Normalizer/DateIntervalNormalizerTest.php
@@ -104,6 +104,14 @@ class DateIntervalNormalizerTest extends TestCase
         $this->assertDateIntervalEquals($this->getInterval($output), $normalizer->denormalize($input, \DateInterval::class));
     }
 
+    public function testDenormalizeIntervalsWithOmittedPartsBeingZero()
+    {
+        $normalizer = new DateIntervalNormalizer();
+
+        $this->assertDateIntervalEquals($this->getInterval('P3Y2M4DT0H0M0S'), $normalizer->denormalize('P3Y2M4D', \DateInterval::class));
+        $this->assertDateIntervalEquals($this->getInterval('P0Y0M0DT12H34M0S'), $normalizer->denormalize('PT12H34M', \DateInterval::class));
+    }
+
     public function testDenormalizeExpectsString()
     {
         $this->expectException(InvalidArgumentException::class);