diff --git a/include/haproxy/thread.h b/include/haproxy/thread.h
index d55c54e..61bae9e 100644
--- a/include/haproxy/thread.h
+++ b/include/haproxy/thread.h
@@ -61,6 +61,7 @@
 enum { threads_want_rdv_mask = 0 };
 enum { tid_bit = 1UL };
 enum { tid = 0 };
+enum { tgid = 1 };
 
 #define HA_SPIN_INIT(l)               do { /* do nothing */ } while(0)
 #define HA_SPIN_DESTROY(l)            do { /* do nothing */ } while(0)
@@ -184,6 +185,7 @@
 extern volatile unsigned long threads_want_rdv_mask;
 extern THREAD_LOCAL unsigned long tid_bit; /* The bit corresponding to the thread id */
 extern THREAD_LOCAL unsigned int tid;      /* The thread id */
+extern THREAD_LOCAL unsigned int tgid;     /* The thread group id (starts at 1) */
 
 /* explanation for threads_want_rdv_mask, threads_harmless_mask, and
  * threads_sync_mask :
@@ -222,13 +224,16 @@
 	if (thr) {
 		BUG_ON(!thr->tid_bit);
 		BUG_ON(!thr->tg);
+		BUG_ON(!thr->tg->tgid);
 
 		ti      = thr;
 		tg      = thr->tg;
 		tid     = thr->tid;
 		tid_bit = thr->tid_bit;
 		th_ctx  = &ha_thread_ctx[tid];
+		tgid    = tg->tgid;
 	} else {
+		tgid    = 1;
 		tid     = 0;
 		tid_bit = 1;
 		ti      = &ha_thread_info[0];
diff --git a/src/thread.c b/src/thread.c
index ce6a476..750702d 100644
--- a/src/thread.c
+++ b/src/thread.c
@@ -66,6 +66,7 @@
 volatile unsigned long threads_idle_mask = 0;
 volatile unsigned long threads_sync_mask = 0;
 volatile unsigned long all_threads_mask __read_mostly  = 1; // nbthread 1 assumed by default
+THREAD_LOCAL unsigned int  tgid          = 1; // thread ID starts at 1
 THREAD_LOCAL unsigned int  tid           = 0;
 THREAD_LOCAL unsigned long tid_bit       = (1UL << 0);
 int thread_cpus_enabled_at_boot          = 1;