diff --git a/composer.json b/composer.json
index b3c2f13dda1..7acdf27f15e 100644
--- a/composer.json
+++ b/composer.json
@@ -14,7 +14,7 @@
         }
     ],
     "require": {
-        "php": "^7.4 || ~8.0.0 || ~8.1.0",
+        "php": "^8.1",
         "ext-SimpleXML": "*",
         "ext-ctype": "*",
         "ext-dom": "*",
diff --git a/src/Psalm/Internal/Analyzer/Statements/Expression/Assignment/ArrayAssignmentAnalyzer.php b/src/Psalm/Internal/Analyzer/Statements/Expression/Assignment/ArrayAssignmentAnalyzer.php
index 619ccd2d755..24a78800d25 100644
--- a/src/Psalm/Internal/Analyzer/Statements/Expression/Assignment/ArrayAssignmentAnalyzer.php
+++ b/src/Psalm/Internal/Analyzer/Statements/Expression/Assignment/ArrayAssignmentAnalyzer.php
@@ -295,7 +295,7 @@ private static function updateTypeWithKeyValues(
         $has_matching_objectlike_property = false;
         $has_matching_string = false;
 
-        $child_stmt_type = clone $child_stmt_type;
+        $child_stmt_type = $child_stmt_type->getBuilder();
 
         foreach ($child_stmt_type->getAtomicTypes() as $type) {
             if ($type instanceof TTemplateParam) {
@@ -351,7 +351,7 @@ private static function updateTypeWithKeyValues(
             }
         }
 
-        $child_stmt_type->bustCache();
+        $child_stmt_type = $child_stmt_type->freeze();
 
         if (!$has_matching_objectlike_property && !$has_matching_string) {
             if (count($key_values) === 1) {
diff --git a/src/Psalm/Type/UnionTrait.php b/src/Psalm/Type/UnionTrait.php
index 3aa2e52199b..feea2ce8b44 100644
--- a/src/Psalm/Type/UnionTrait.php
+++ b/src/Psalm/Type/UnionTrait.php
@@ -344,6 +344,12 @@ public function getKey(): string
         return implode('|', $types);
     }
 
+    public function bustCache(): void
+    {
+        $this->id = null;
+        $this->exact_id = null;
+    }
+
     public function getId(bool $exact = true): string
     {
         if ($exact && $this->exact_id) {