diff --git a/src/Symfony/Component/TypeInfo/Tests/TypeResolver/StringTypeResolverTest.php b/src/Symfony/Component/TypeInfo/Tests/TypeResolver/StringTypeResolverTest.php
index fcfe909cecf6e..a87c7b37f3f8e 100644
--- a/src/Symfony/Component/TypeInfo/Tests/TypeResolver/StringTypeResolverTest.php
+++ b/src/Symfony/Component/TypeInfo/Tests/TypeResolver/StringTypeResolverTest.php
@@ -79,6 +79,7 @@ public static function resolveDataProvider(): iterable
         yield [Type::arrayShape(['foo' => Type::bool()], sealed: false), 'array{foo: bool, ...}'];
         yield [Type::arrayShape(['foo' => Type::bool()], extraKeyType: Type::int(), extraValueType: Type::string()), 'array{foo: bool, ...<int, string>}'];
         yield [Type::arrayShape(['foo' => Type::bool()], extraValueType: Type::int()), 'array{foo: bool, ...<int>}'];
+        yield [Type::arrayShape(['foo' => Type::union(Type::bool(), Type::float(), Type::int(), Type::null(), Type::string()), 'bar' => Type::string()]), 'array{foo: scalar|null, bar: string}'];
 
         // object shape
         yield [Type::object(), 'object{foo: true, bar: false}'];
diff --git a/src/Symfony/Component/TypeInfo/Type/CollectionType.php b/src/Symfony/Component/TypeInfo/Type/CollectionType.php
index 80fbbdba6c3fa..a801f2b51f8d0 100644
--- a/src/Symfony/Component/TypeInfo/Type/CollectionType.php
+++ b/src/Symfony/Component/TypeInfo/Type/CollectionType.php
@@ -65,25 +65,27 @@ public static function mergeCollectionValueTypes(array $types): Type
         $boolTypes = [];
         $objectTypes = [];
 
-        foreach ($types as $t) {
-            // cannot create an union with a standalone type
-            if ($t->isIdentifiedBy(TypeIdentifier::MIXED)) {
-                return Type::mixed();
-            }
+        foreach ($types as $type) {
+            foreach (($type instanceof UnionType ? $type->getTypes() : [$type]) as $t) {
+                // cannot create an union with a standalone type
+                if ($t->isIdentifiedBy(TypeIdentifier::MIXED)) {
+                    return Type::mixed();
+                }
 
-            if ($t->isIdentifiedBy(TypeIdentifier::TRUE, TypeIdentifier::FALSE, TypeIdentifier::BOOL)) {
-                $boolTypes[] = $t;
+                if ($t->isIdentifiedBy(TypeIdentifier::TRUE, TypeIdentifier::FALSE, TypeIdentifier::BOOL)) {
+                    $boolTypes[] = $t;
 
-                continue;
-            }
+                    continue;
+                }
 
-            if ($t->isIdentifiedBy(TypeIdentifier::OBJECT)) {
-                $objectTypes[] = $t;
+                if ($t->isIdentifiedBy(TypeIdentifier::OBJECT)) {
+                    $objectTypes[] = $t;
 
-                continue;
-            }
+                    continue;
+                }
 
-            $normalizedTypes[] = $t;
+                $normalizedTypes[] = $t;
+            }
         }
 
         $boolTypes = array_unique($boolTypes);