diff --git a/NEWS b/NEWS
index 355ae1d5b8d91..c8ded9b60515d 100644
--- a/NEWS
+++ b/NEWS
@@ -12,6 +12,8 @@ PHP                                                                        NEWS
   . SA_ONSTACK is now set for signal handlers to be friendlier to other
     in-process code such as Go's cgo. (Kévin Dunglas)
   . SA_ONSTACK is now set when signals are disabled. (Kévin Dunglas)
+  . Fix GH-9649: Signal handlers now do a no-op instead of crashing when
+    executed on threads not managed by TSRM. (Kévin Dunglas)
 
 - Fileinfo:
   . Upgrade bundled libmagic to 5.43. (Anatol)
diff --git a/TSRM/TSRM.c b/TSRM/TSRM.c
index 0c6daedf399c8..76ffe3fb3376f 100644
--- a/TSRM/TSRM.c
+++ b/TSRM/TSRM.c
@@ -779,4 +779,9 @@ TSRM_API const char *tsrm_api_name(void)
 #endif
 }/*}}}*/
 
+TSRM_API bool tsrm_is_managed_thread()
+{/*{{{*/
+	return tsrm_tls_get() ? true : false;
+}/*}}}*/
+
 #endif /* ZTS */
diff --git a/TSRM/TSRM.h b/TSRM/TSRM.h
index 60b65ca8ec762..3bb32e4da289a 100644
--- a/TSRM/TSRM.h
+++ b/TSRM/TSRM.h
@@ -137,6 +137,7 @@ TSRM_API size_t tsrm_get_ls_cache_tcb_offset(void);
 TSRM_API bool tsrm_is_main_thread(void);
 TSRM_API bool tsrm_is_shutdown(void);
 TSRM_API const char *tsrm_api_name(void);
+TSRM_API bool tsrm_is_managed_thread(void);
 
 #ifdef TSRM_WIN32
 # define TSRM_TLS __declspec(thread)
diff --git a/Zend/zend_execute_API.c b/Zend/zend_execute_API.c
index c7ccfc5a91ccc..235a8fe8a79cc 100644
--- a/Zend/zend_execute_API.c
+++ b/Zend/zend_execute_API.c
@@ -1355,7 +1355,13 @@ ZEND_API ZEND_NORETURN void ZEND_FASTCALL zend_timeout(void) /* {{{ */
 #ifndef ZEND_WIN32
 static void zend_timeout_handler(int dummy) /* {{{ */
 {
-#ifndef ZTS
+#ifdef ZTS
+	if (!tsrm_is_managed_thread()) {
+		fprintf(stderr, "zend_timeout_handler() called in a thread not managed by PHP. The expected signal handler will not be called. This is probably a bug.\n");
+
+		return;
+	}
+#else
 	if (zend_atomic_bool_load_ex(&EG(timed_out))) {
 		/* Die on hard timeout */
 		const char *error_filename = NULL;
diff --git a/Zend/zend_signal.c b/Zend/zend_signal.c
index be48a91d3d88b..fc913b72f0641 100644
--- a/Zend/zend_signal.c
+++ b/Zend/zend_signal.c
@@ -87,6 +87,12 @@ void zend_signal_handler_defer(int signo, siginfo_t *siginfo, void *context)
 	zend_signal_queue_t *queue, *qtmp;
 
 #ifdef ZTS
+	if (!tsrm_is_managed_thread()) {
+		fprintf(stderr, "zend_signal_handler_defer() called in a thread not managed by PHP. The expected signal handler will not be called. This is probably a bug.\n");
+
+		return;
+	}
+
 	/* A signal could hit after TSRM shutdown, in this case globals are already freed. */
 	if (tsrm_is_shutdown()) {
 		/* Forward to default handler handler */