diff --git a/Zend/tests/gh12366.inc b/Zend/tests/gh12366.inc
new file mode 100644
index 00000000000..c0f64e14ba7
--- /dev/null
+++ b/Zend/tests/gh12366.inc
@@ -0,0 +1,7 @@
+<?php
+
+enum Level: int {
+    case Debug = 100;
+}
+
+var_dump(Level::Debug);
diff --git a/Zend/tests/gh12366.phpt b/Zend/tests/gh12366.phpt
new file mode 100644
index 00000000000..1d272baf578
--- /dev/null
+++ b/Zend/tests/gh12366.phpt
@@ -0,0 +1,16 @@
+--TEST--
+GH-12366: Use-after-free of constant name when script doesn't fit in SHM
+--EXTENSIONS--
+opcache
+--INI--
+opcache.enable_cli=1
+opcache.file_update_protection=1
+--FILE--
+<?php
+$file = __DIR__ . '/gh12366.inc';
+// Update timestamp and use opcache.file_update_protection=1 to prevent included file from being persisted in shm.
+touch($file);
+require $file;
+?>
+--EXPECT--
+enum(Level::Debug)
diff --git a/Zend/zend_enum.c b/Zend/zend_enum.c
index 2e85bb08a72..58862c1564d 100644
--- a/Zend/zend_enum.c
+++ b/Zend/zend_enum.c
@@ -236,6 +236,7 @@ zend_result zend_enum_build_backed_enum_table(zend_class_entry *ce)
 					ZSTR_VAL(name));
 				goto failure;
 			}
+			Z_TRY_ADDREF_P(case_name);
 			zend_hash_index_add_new(backed_enum_table, long_key, case_name);
 		} else {
 			ZEND_ASSERT(ce->enum_backing_type == IS_STRING);
@@ -248,6 +249,7 @@ zend_result zend_enum_build_backed_enum_table(zend_class_entry *ce)
 					ZSTR_VAL(name));
 				goto failure;
 			}
+			Z_TRY_ADDREF_P(case_name);
 			zend_hash_add_new(backed_enum_table, string_key, case_name);
 		}
 	} ZEND_HASH_FOREACH_END();