diff --git a/NEWS b/NEWS
index ba1164f2e21..941be6c0a84 100644
--- a/NEWS
+++ b/NEWS
@@ -73,6 +73,9 @@ PHP                                                                        NEWS
   . Added X509_PURPOSE_OCSP_HELPER and X509_PURPOSE_TIMESTAMP_SIGN constants.
     (Vincent Jardin)
 
+- Output:
+  . Clear output handler status flags during handler initialization. (haszi)
+
 - PDO:
   . Fixed setAttribute and getAttribute. (SakiTakamachi)
   . Implemented PDO driver-specific subclasses RFC. (danack, kocsismate)
diff --git a/UPGRADING b/UPGRADING
index 24f4e5f0ecc..4b2e14fb5ae 100644
--- a/UPGRADING
+++ b/UPGRADING
@@ -313,6 +313,10 @@ PHP 8.4 UPGRADE NOTES
   . New serial_hex parameter added to openssl_csr_sign to allow setting serial
     number in the hexadecimal format.
 
+- Output:
+  . Output handler status flags passed to the flags parameter of ob_start
+    are now cleared.
+
 - PDO:
   . getAttribute, enabled to get the value of ATTR_STRINGIFY_FETCHES.
 
diff --git a/main/output.c b/main/output.c
index 76d4e7709e8..2c2c13b672a 100644
--- a/main/output.c
+++ b/main/output.c
@@ -478,7 +478,7 @@ PHPAPI php_output_handler *php_output_handler_create_user(zval *output_handler,
 		default:
 			user = ecalloc(1, sizeof(php_output_handler_user_func_t));
 			if (SUCCESS == zend_fcall_info_init(output_handler, 0, &user->fci, &user->fcc, &handler_name, &error)) {
-				handler = php_output_handler_init(handler_name, chunk_size, (flags & ~0xf) | PHP_OUTPUT_HANDLER_USER);
+				handler = php_output_handler_init(handler_name, chunk_size, PHP_OUTPUT_HANDLER_ABILITY_FLAGS(flags) | PHP_OUTPUT_HANDLER_USER);
 				ZVAL_COPY(&user->zoh, output_handler);
 				handler->func.user = user;
 			} else {
@@ -504,7 +504,7 @@ PHPAPI php_output_handler *php_output_handler_create_internal(const char *name,
 	php_output_handler *handler;
 	zend_string *str = zend_string_init(name, name_len, 0);
 
-	handler = php_output_handler_init(str, chunk_size, (flags & ~0xf) | PHP_OUTPUT_HANDLER_INTERNAL);
+	handler = php_output_handler_init(str, chunk_size, PHP_OUTPUT_HANDLER_ABILITY_FLAGS(flags) | PHP_OUTPUT_HANDLER_INTERNAL);
 	handler->func.internal = output_handler;
 	zend_string_release_ex(str, 0);
 
diff --git a/main/php_output.h b/main/php_output.h
index 852aab7fb9d..d722eba953b 100644
--- a/main/php_output.h
+++ b/main/php_output.h
@@ -43,6 +43,8 @@
 #define PHP_OUTPUT_HANDLER_DISABLED		0x2000
 #define PHP_OUTPUT_HANDLER_PROCESSED	0x4000
 
+#define PHP_OUTPUT_HANDLER_ABILITY_FLAGS(bitmask) ((bitmask) & ~0xf00f)
+
 /* handler op return values */
 typedef enum _php_output_handler_status_t {
 	PHP_OUTPUT_HANDLER_FAILURE,
diff --git a/tests/output/ob_start_flags.phpt b/tests/output/ob_start_flags.phpt
new file mode 100644
index 00000000000..a52ced6bd10
--- /dev/null
+++ b/tests/output/ob_start_flags.phpt
@@ -0,0 +1,31 @@
+--TEST--
+ob_start(): Ensure that user supplied handler type and status flags are erased
+--FILE--
+<?php
+define('PHP_OUTPUT_HANDLER_TYPE_INTERNAL', 0);
+define('PHP_OUTPUT_HANDLER_TYPE_USER', 1);
+
+ob_start(
+    fn ($s) => $s,
+    0,
+    PHP_OUTPUT_HANDLER_STDFLAGS |
+    PHP_OUTPUT_HANDLER_TYPE_INTERNAL |
+    PHP_OUTPUT_HANDLER_STARTED |
+    PHP_OUTPUT_HANDLER_DISABLED |
+    PHP_OUTPUT_HANDLER_PROCESSED
+);
+
+$bitmask = ob_get_status()['flags'];
+
+var_dump($bitmask & PHP_OUTPUT_HANDLER_STDFLAGS);
+var_dump($bitmask & PHP_OUTPUT_HANDLER_TYPE_USER);
+var_dump($bitmask & PHP_OUTPUT_HANDLER_STARTED);
+var_dump($bitmask & PHP_OUTPUT_HANDLER_DISABLED);
+var_dump($bitmask & PHP_OUTPUT_HANDLER_PROCESSED);
+?>
+--EXPECT--
+int(112)
+int(1)
+int(0)
+int(0)
+int(0)