diff --git a/include/haproxy/tinfo-t.h b/include/haproxy/tinfo-t.h
index e2779ab10..ba2424975 100644
--- a/include/haproxy/tinfo-t.h
+++ b/include/haproxy/tinfo-t.h
@@ -46,6 +46,7 @@ enum {
 struct tgroup_info {
 	uint base;                 /* first thread in this group */
 	uint count;                /* number of threads in this group */
+	uint tgid;                 /* group ID (starts at 1, 0=unspecified) */
 
 	/* pad to cache line (64B) */
 	char __pad[0];            /* unused except to check remaining room */
diff --git a/src/thread.c b/src/thread.c
index 2a7d3aff3..0b979f912 100644
--- a/src/thread.c
+++ b/src/thread.c
@@ -1019,6 +1019,7 @@ int thread_map_to_groups()
 	for (g = 0; g < global.nbtgroups; g++) {
 		if (!ha_tgroup_info[g].count)
 			ug++;
+		ha_tgroup_info[g].tgid = g + 1;
 	}
 
 	if (ug > ut) {