diff --git a/sapi/cgi/cgi_main.c b/sapi/cgi/cgi_main.c
index 156599f6f9d4d..695a693019821 100644
--- a/sapi/cgi/cgi_main.c
+++ b/sapi/cgi/cgi_main.c
@@ -355,11 +355,11 @@ static void sapi_fcgi_flush(void *server_context)
 {
 	fcgi_request *request = (fcgi_request*) server_context;
 
-	if (
-		!parent &&
-		request && !fcgi_flush(request, 0)) {
-
-		php_handle_aborted_connection();
+	if (!parent && request) {
+		sapi_send_headers();
+		if (!fcgi_flush(request, 0)) {
+			php_handle_aborted_connection();
+		}
 	}
 }
 
diff --git a/sapi/fpm/fpm/fpm_main.c b/sapi/fpm/fpm/fpm_main.c
index b3ae2f69cc556..12709ae063ab9 100644
--- a/sapi/fpm/fpm/fpm_main.c
+++ b/sapi/fpm/fpm/fpm_main.c
@@ -291,8 +291,11 @@ static void sapi_cgibin_flush(void *server_context) /* {{{ */
 	/* fpm has started, let use fcgi instead of stdout */
 	if (fpm_is_running) {
 		fcgi_request *request = (fcgi_request*) server_context;
-		if (!parent && request && !fcgi_flush(request, 0)) {
-			php_handle_aborted_connection();
+		if (!parent && request) {
+			sapi_send_headers();
+			if (!fcgi_flush(request, 0)) {
+				php_handle_aborted_connection();
+			}
 		}
 		return;
 	}
diff --git a/sapi/fpm/tests/gh12385.phpt b/sapi/fpm/tests/gh12385.phpt
new file mode 100644
index 0000000000000..08b9882616679
--- /dev/null
+++ b/sapi/fpm/tests/gh12385.phpt
@@ -0,0 +1,46 @@
+--TEST--
+GH-12385 (flush with fastcgi does not force headers to be sent)
+--SKIPIF--
+<?php
+include "skipif.inc";
+?>
+--FILE--
+<?php
+
+require_once "tester.inc";
+
+$cfg = <<<EOT
+[global]
+error_log = {{FILE:LOG}}
+[unconfined]
+listen = {{ADDR}}
+pm = static
+pm.max_children = 1
+EOT;
+
+$code = <<<PHP
+<?php
+header("X-Test: 12345");
+flush();
+var_dump(headers_sent());
+PHP;
+
+$tester = new FPM\Tester($cfg, $code);
+$tester->start();
+$tester->expectLogStartNotices();
+$response = $tester->request();
+$response->expectHeader("X-Test", "12345");
+$response->expectBody("bool(true)");
+$tester->terminate();
+$tester->expectLogTerminatingNotices();
+$tester->close();
+
+?>
+Done
+--EXPECT--
+Done
+--CLEAN--
+<?php
+require_once "tester.inc";
+FPM\Tester::clean();
+?>