diff --git a/core/models/groups.go b/core/models/groups.go
index 5a391c60d..ce8ab590b 100644
--- a/core/models/groups.go
+++ b/core/models/groups.go
@@ -376,7 +376,7 @@ func PopulateDynamicGroup(ctx context.Context, db *sqlx.DB, es *elastic.Client,
 		return 0, errors.Wrapf(err, "error performing query: %s for group: %d", query, groupID)
 	}
 
-	// find which need to be added or removed
+	// find which contacts need to be added or removed
 	adds := make([]ContactID, 0, 100)
 	for _, id := range new {
 		if !present[id] {
@@ -409,5 +409,15 @@ func PopulateDynamicGroup(ctx context.Context, db *sqlx.DB, es *elastic.Client,
 		return 0, errors.Wrapf(err, "error marking dynamic group as ready")
 	}
 
+	// finally update modified_on for all affected contacts to ensure these changes are seen by rp-indexer
+	changed := make([]ContactID, 0, len(adds))
+	changed = append(changed, adds...)
+	changed = append(changed, removals...)
+
+	err = UpdateContactModifiedOn(ctx, db, changed)
+	if err != nil {
+		return 0, errors.Wrapf(err, "error updating contact modified_on after group population")
+	}
+
 	return len(new), nil
 }
diff --git a/core/tasks/contacts/populate_dynamic_group_test.go b/core/tasks/contacts/populate_dynamic_group_test.go
index c4cc38484..686ede1ee 100644
--- a/core/tasks/contacts/populate_dynamic_group_test.go
+++ b/core/tasks/contacts/populate_dynamic_group_test.go
@@ -4,6 +4,7 @@ import (
 	"fmt"
 	"testing"
 
+	"github.com/nyaruka/gocommon/dates"
 	"github.com/nyaruka/mailroom/core/tasks/contacts"
 	"github.com/nyaruka/mailroom/testsuite"
 	"github.com/nyaruka/mailroom/testsuite/testdata"
@@ -52,6 +53,7 @@ func TestPopulateTask(t *testing.T) {
 	}`, testdata.Cathy.ID)
 
 	group := testdata.InsertContactGroup(db, testdata.Org1, "e52fee05-2f95-4445-aef6-2fe7dac2fd56", "Women", "gender = F")
+	start := dates.Now()
 
 	task := &contacts.PopulateDynamicGroupTask{
 		GroupID: group.ID,
@@ -61,4 +63,6 @@ func TestPopulateTask(t *testing.T) {
 	require.NoError(t, err)
 
 	testsuite.AssertQuery(t, db, `SELECT count(*) FROM contacts_contactgroup_contacts WHERE contactgroup_id = $1`, group.ID).Returns(1)
+	testsuite.AssertQuery(t, db, `SELECT contact_id FROM contacts_contactgroup_contacts WHERE contactgroup_id = $1`, group.ID).Returns(int64(testdata.Cathy.ID))
+	testsuite.AssertQuery(t, db, `SELECT count(*) FROM contacts_contact WHERE id = $1 AND modified_on > $2`, testdata.Cathy.ID, start).Returns(1)
 }