diff -up thunderbird-145.0/security/sandbox/chromium/sandbox/linux/system_headers/linux_seccomp.h.seccomp thunderbird-145.0/security/sandbox/chromium/sandbox/linux/system_headers/linux_seccomp.h
--- thunderbird-145.0/security/sandbox/chromium/sandbox/linux/system_headers/linux_seccomp.h.seccomp	2025-12-09 13:42:31.378958842 +0100
+++ thunderbird-145.0/security/sandbox/chromium/sandbox/linux/system_headers/linux_seccomp.h	2025-12-09 13:42:37.886937626 +0100
@@ -6,6 +6,7 @@
 #define SANDBOX_LINUX_SYSTEM_HEADERS_LINUX_SECCOMP_H_
 
 #include <stdint.h>
+#include <signal.h>
 #include <sys/ioctl.h>
 
 #include "build/build_config.h"