diff --git a/src/wdt.c b/src/wdt.c
index fab1269f0..20297bcb9 100644
--- a/src/wdt.c
+++ b/src/wdt.c
@@ -53,6 +53,7 @@ int wdt_ping(int thr)
 void wdt_handler(int sig, siginfo_t *si, void *arg)
 {
 	unsigned long long n, p;
+	ulong thr_bit;
 	int thr;
 
 	switch (si->si_code) {
@@ -71,6 +72,7 @@ void wdt_handler(int sig, siginfo_t *si, void *arg)
 		if (thr < 0 || thr >= global.nbthread)
 			break;
 
+		thr_bit = ha_thread_info[thr].ltid_bit;
 		p = ha_thread_ctx[thr].prev_cpu_time;
 		n = now_cpu_time_thread(thr);
 
@@ -81,7 +83,7 @@ void wdt_handler(int sig, siginfo_t *si, void *arg)
 			goto update_and_leave;
 
 		if ((_HA_ATOMIC_LOAD(&th_ctx->flags) & TH_FL_SLEEPING) &&
-		    ((threads_harmless_mask|threads_to_dump) & (1UL << thr))) {
+		    ((threads_harmless_mask|threads_to_dump) & thr_bit)) {
 			/* This thread is currently doing exactly nothing
 			 * waiting in the poll loop (unlikely but possible),
 			 * waiting for all other threads to join the rendez-vous