diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index 3d843be0..41f461e9 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -237,7 +237,7 @@ jobs:
       - name: Run compiler PHPT suite with bootstrap compiler
         run: |
           mkdir -p build
-          php run-tests.php -q -j8 --compiler ./tpc \
+          php run-tests.php -q -j4 --compiler ./tpc \
             -w build/failed-tests.txt -W build/test-results.txt tests/compiler
 
       - name: Upload PHPT failure artifacts
diff --git a/phpunit/src/GenStubVersionFlagsTest.php b/phpunit/src/GenStubVersionFlagsTest.php
index ed7d46ec..658fbeb5 100644
--- a/phpunit/src/GenStubVersionFlagsTest.php
+++ b/phpunit/src/GenStubVersionFlagsTest.php
@@ -2,6 +2,27 @@
 
 final class GenStubVersionFlagsTest extends BaseTest
 {
+    public function testPersistentStringMetadataUsesANonRefcountedInternedZval(): void
+    {
+        global $translator;
+        $translator = \TypePhp\CompilerTest::create(ROOT_PATH);
+
+        $value = EvaluatedValue::createFromExpression(
+            new PhpParser\Node\Scalar\String_('PHP'),
+            null,
+            null,
+            [],
+        );
+
+        $code = $value->initializeZval('property_lang_default_value');
+
+        self::assertStringContainsString('zend_string_init_interned("PHP"', $code);
+        self::assertStringContainsString(
+            'ZVAL_INTERNED_STR(&property_lang_default_value, property_lang_default_value_str);',
+            $code,
+        );
+    }
+
     public function testFlagIntroducedBeforeMinimumSupportedVersionRemainsEnabled(): void
     {
         $flags = new VersionFlags(['ZEND_ACC_PRIVATE']);
diff --git a/src/gen_stub.php b/src/gen_stub.php
index 00b2c04b..c39335b6 100755
--- a/src/gen_stub.php
+++ b/src/gen_stub.php
@@ -2753,8 +2753,12 @@ class EvaluatedValue
                 }
                 // getCExpr() emits a C string literal here. sizeof() preserves
                 // embedded NUL bytes, unlike strlen().
-                $code .= "\tzend_string *$forStringDef = zend_string_init($cExpr, sizeof($cExpr) - 1, 1);\n";
-                $code .= "\tZVAL_STR(&$zvalName, $forStringDef);\n";
+                // Internal class metadata is persistent. PHP 8.5 rejects
+                // refcounted zvals in persistent property defaults, so a
+                // persistent-but-refcounted zend_string is not sufficient.
+                // Interning also makes the value safe to share under ZTS.
+                $code .= "\tzend_string *$forStringDef = zend_string_init_interned($cExpr, sizeof($cExpr) - 1, 1);\n";
+                $code .= "\tZVAL_INTERNED_STR(&$zvalName, $forStringDef);\n";
             }
         } elseif ($this->type->isArray()) {
             $code .= "\tZVAL_EMPTY_ARRAY(&$zvalName);\n";