diff --git a/include/haproxy/tinfo-t.h b/include/haproxy/tinfo-t.h
index 7ed05651a..62e87f87e 100644
--- a/include/haproxy/tinfo-t.h
+++ b/include/haproxy/tinfo-t.h
@@ -42,7 +42,7 @@ struct thread_set {
 		ulong abs[(MAX_THREADS + LONGBITS - 1) / LONGBITS];
 		ulong rel[MAX_TGROUPS];
 	};
-	ulong grps; /* bit field of all non-empty groups, 0 for abs */
+	ulong nbgrps; /* Number of thread groups, 0 for abs */
 };
 
 /* tasklet classes */
diff --git a/include/haproxy/tinfo.h b/include/haproxy/tinfo.h
index ddb26aac7..a6497f558 100644
--- a/include/haproxy/tinfo.h
+++ b/include/haproxy/tinfo.h
@@ -77,7 +77,7 @@ static inline int thread_set_nth_group(const struct thread_set *ts, int n)
 {
 	int i;
 
-	if (ts->grps) {
+	if (ts->nbgrps) {
 		for (i = 0; i < MAX_TGROUPS; i++)
 			if (ts->rel[i] && !n--)
 				return i + 1;
@@ -95,7 +95,7 @@ static inline ulong thread_set_nth_tmask(const struct thread_set *ts, int n)
 {
 	int i;
 
-	if (ts->grps) {
+	if (ts->nbgrps) {
 		for (i = 0; i < MAX_TGROUPS; i++)
 			if (ts->rel[i] && !n--)
 				return ts->rel[i];
@@ -111,7 +111,7 @@ static inline void thread_set_pin_grp1(struct thread_set *ts, ulong mask)
 {
 	int i;
 
-	ts->grps = 1;
+	ts->nbgrps = 1;
 	ts->rel[0] = mask;
 	for (i = 1; i < MAX_TGROUPS; i++)
 		ts->rel[i] = 0;
diff --git a/src/listener.c b/src/listener.c
index 9dd01250f..5b5d0f2fa 100644
--- a/src/listener.c
+++ b/src/listener.c
@@ -1756,7 +1756,8 @@ int bind_complete_thread_setup(struct bind_conf *bind_conf, int *err_code)
 	struct listener *li, *new_li, *ref;
 	struct thread_set new_ts;
 	int shard, shards, todo, done, grp, dups;
-	ulong mask, gmask, bit;
+	ulong mask, bit;
+	int nbgrps;
 	int cfgerr = 0;
 	char *err;
 
@@ -1788,7 +1789,7 @@ int bind_complete_thread_setup(struct bind_conf *bind_conf, int *err_code)
 			}
 		}
 		else if (shards == -2)
-			shards = protocol_supports_flag(li->rx.proto, PROTO_F_REUSEPORT_SUPPORTED) ? my_popcountl(bind_conf->thread_set.grps) : 1;
+			shards = protocol_supports_flag(li->rx.proto, PROTO_F_REUSEPORT_SUPPORTED) ? bind_conf->thread_set.nbgrps : 1;
 
 		/* no more shards than total threads */
 		if (shards > todo)
@@ -1821,25 +1822,25 @@ int bind_complete_thread_setup(struct bind_conf *bind_conf, int *err_code)
 
 				/* take next unassigned bit */
 				bit = (bind_conf->thread_set.rel[grp] & ~mask) & -(bind_conf->thread_set.rel[grp] & ~mask);
+				if (!new_ts.rel[grp])
+					new_ts.nbgrps++;
 				new_ts.rel[grp] |= bit;
 				mask |= bit;
-				new_ts.grps |= 1UL << grp;
 
 				done += shards;
 			};
 
-			BUG_ON(!new_ts.grps); // no more bits left unassigned
+			BUG_ON(!new_ts.nbgrps); // no more group ?
 
 			/* Create all required listeners for all bound groups. If more than one group is
 			 * needed, the first receiver serves as a reference, and subsequent ones point to
 			 * it. We already have a listener available in new_li() so we only allocate a new
-			 * one if we're not on the last one. We count the remaining groups by copying their
-			 * mask into <gmask> and dropping the lowest bit at the end of the loop until there
-			 * is no more. Ah yes, it's not pretty :-/
+			 * one if we're not on the last one.
+			 *
 			 */
 			ref = new_li;
-			gmask = new_ts.grps;
-			for (dups = 0; gmask; dups++) {
+			nbgrps = new_ts.nbgrps;
+			for (dups = 0; nbgrps; dups++) {
 				/* assign the first (and only) thread and group */
 				new_li->rx.bind_thread = thread_set_nth_tmask(&new_ts, dups);
 				new_li->rx.bind_tgroup = thread_set_nth_group(&new_ts, dups);
@@ -1856,8 +1857,8 @@ int bind_complete_thread_setup(struct bind_conf *bind_conf, int *err_code)
 					new_li->rx.flags |= ref->rx.flags & RX_F_INHERITED_SOCK;
 				}
 
-				gmask &= gmask - 1; // drop lowest bit
-				if (gmask) {
+				nbgrps--;
+				if (nbgrps) {
 					/* yet another listener expected in this shard, let's
 					 * chain it.
 					 */
@@ -2672,7 +2673,7 @@ static int bind_parse_thread(char **args, int cur_arg, struct proxy *px, struct
 
 	l = LIST_NEXT(&conf->listeners, struct listener *, by_bind);
 	if (l->rx.addr.ss_family == AF_CUST_RHTTP_SRV &&
-	    atleast2(conf->thread_set.grps)) {
+	    conf->thread_set.nbgrps >= 2) {
 		memprintf(err, "'%s' : reverse HTTP bind cannot span multiple thread groups.", args[cur_arg]);
 		return ERR_ALERT | ERR_FATAL;
 	}
diff --git a/src/thread.c b/src/thread.c
index 159d40506..c156d84e5 100644
--- a/src/thread.c
+++ b/src/thread.c
@@ -1524,7 +1524,7 @@ int thread_resolve_group_mask(struct thread_set *ts, int defgrp, char **err)
 	ulong mask, imask;
 	uint g;
 
-	if (!ts->grps) {
+	if (!ts->nbgrps) {
 		/* unspecified group, IDs are global */
 		if (thread_set_is_empty(ts)) {
 			/* all threads of all groups, unless defgrp is set and
@@ -1533,7 +1533,7 @@ int thread_resolve_group_mask(struct thread_set *ts, int defgrp, char **err)
 			for (g = defgrp ? defgrp-1 : 0; g < (defgrp ? defgrp : global.nbtgroups); g++) {
 				new_ts.rel[g] = ha_tgroup_info[g].threads_enabled;
 				if (new_ts.rel[g])
-					new_ts.grps |= 1UL << g;
+					new_ts.nbgrps++;
 			}
 		} else {
 			/* some absolute threads are set, we must remap them to
@@ -1558,7 +1558,7 @@ int thread_resolve_group_mask(struct thread_set *ts, int defgrp, char **err)
 				 */
 				new_ts.rel[g] |= mask;
 				if (new_ts.rel[g])
-					new_ts.grps |= 1UL << g;
+					new_ts.nbgrps++;
 			}
 		}
 	} else {
@@ -1596,7 +1596,7 @@ int thread_resolve_group_mask(struct thread_set *ts, int defgrp, char **err)
 
 			new_ts.rel[g] = imask & mask;
 			if (new_ts.rel[g])
-				new_ts.grps |= 1UL << g;
+				new_ts.nbgrps++;
 		}
 	}
 
@@ -1943,7 +1943,8 @@ int parse_thread_set(const char *arg, struct thread_set *ts, char **err)
 		if (ts) {
 			if (is_rel) {
 				/* group-relative thread numbers */
-				ts->grps |= 1UL << (tg - 1);
+				if (ts->rel[tg - 1] == 0)
+					ts->nbgrps++;
 
 				if (max >= min) {
 					for (v = min; v <= max; v++)