diff --git a/Zend/tests/ctor_promotion/ctor_promotion_final.phpt b/Zend/tests/ctor_promotion/ctor_promotion_final.phpt
new file mode 100644
index 00000000000..abfb5b70880
--- /dev/null
+++ b/Zend/tests/ctor_promotion/ctor_promotion_final.phpt
@@ -0,0 +1,23 @@
+--TEST--
+GH-20377: Constructor promotion with a final property without visibility set
+--FILE--
+<?php
+
+class Demo {
+    public function __construct(
+        final string $foo,
+        final public string $bar,
+    ) {}
+}
+
+$d = new Demo("first", "second");
+var_dump($d);
+
+?>
+--EXPECTF--
+object(Demo)#%d (2) {
+  ["foo"]=>
+  string(5) "first"
+  ["bar"]=>
+  string(6) "second"
+}
diff --git a/Zend/zend_compile.c b/Zend/zend_compile.c
index 4632a3fca18..50ba8029873 100644
--- a/Zend/zend_compile.c
+++ b/Zend/zend_compile.c
@@ -7864,6 +7864,7 @@ static void zend_compile_params(zend_ast *ast, zend_ast *return_type_ast, uint32
 		}
 	}
 
+	const uint32_t promotion_flags = ZEND_ACC_PPP_MASK | ZEND_ACC_PPP_SET_MASK | ZEND_ACC_READONLY | ZEND_ACC_FINAL;
 	for (i = 0; i < list->children; ++i) {
 		zend_ast *param_ast = list->child[i];
 		zend_ast *type_ast = param_ast->child[0];
@@ -7875,7 +7876,7 @@ static void zend_compile_params(zend_ast *ast, zend_ast *return_type_ast, uint32
 		zend_string *name = zval_make_interned_string(zend_ast_get_zval(var_ast));
 		bool is_ref = (param_ast->attr & ZEND_PARAM_REF) != 0;
 		bool is_variadic = (param_ast->attr & ZEND_PARAM_VARIADIC) != 0;
-		uint32_t property_flags = param_ast->attr & (ZEND_ACC_PPP_MASK | ZEND_ACC_PPP_SET_MASK | ZEND_ACC_READONLY | ZEND_ACC_FINAL);
+		uint32_t property_flags = param_ast->attr & promotion_flags;
 		bool is_promoted = property_flags || hooks_ast;
 
 		CG(zend_lineno) = param_ast->lineno;
@@ -8102,7 +8103,7 @@ static void zend_compile_params(zend_ast *ast, zend_ast *return_type_ast, uint32
 		zend_ast *param_ast = list->child[i];
 		zend_ast *hooks_ast = param_ast->child[5];
 		bool is_ref = (param_ast->attr & ZEND_PARAM_REF) != 0;
-		uint32_t flags = param_ast->attr & (ZEND_ACC_PPP_MASK | ZEND_ACC_PPP_SET_MASK | ZEND_ACC_READONLY);
+		uint32_t flags = param_ast->attr & promotion_flags;
 		bool is_promoted = flags || hooks_ast;
 		if (!is_promoted) {
 			continue;