diff --git a/docs/SHADE_BEHAVIOUR_PLAN.md b/docs/SHADE_BEHAVIOUR_PLAN.md
index ca06fe6..e669c75 100644
--- a/docs/SHADE_BEHAVIOUR_PLAN.md
+++ b/docs/SHADE_BEHAVIOUR_PLAN.md
@@ -89,7 +89,7 @@ The decisions are the user's. Each question comes with a recommended answer, and
   - Up and My on tilt-only shades differ between the web, a remote and a group (`test_today_up_on_tilt_only_*`, `test_today_my_while_tilt_only_moves`).
   - An integrated tilt sent to a lift target without a tilt turns its slats back with an Up after the stop (`test_today_integrated_tilt_turns_back_after_a_lift_target`).
   - ~~A remote step uses the step size this shade last *sent*.~~ Fixed (Q19).
-  - A group's SunFlag or Flag doesn't make other groups work their flags out again (`test_group_sun_flag_needs_a_sensor`).
+  - ~~A group's SunFlag or Flag doesn't make other groups work their flags out again.~~ Fixed (Q20).
   - The self-echo (Q5) and merging group commands into the frame rule (Q8).
   - `lastFrame` doing two jobs (the Q6 revisit).
   - The 500 ms long-press deadline is compared as `now > await`, which isn't wrap-safe (not tested).
diff --git a/src/ShadeBehaviour.cpp b/src/ShadeBehaviour.cpp
index 22b1c83..42745b7 100644
--- a/src/ShadeBehaviour.cpp
+++ b/src/ShadeBehaviour.cpp
@@ -786,6 +786,8 @@ void ShadeBehaviour::onGroupCommand(somfy_commands cmd, uint8_t repeat, uint32_t
       break;
     case somfy_commands::Flag:
       this->p_sunFlag(false);
+      // Every group works its flags out again, as for a Flag frame.
+      this->events.onSensorFlags();
       if(this->settings.sunSensor) {
         this->events.onSaveWanted();
         this->emitState();
@@ -803,6 +805,7 @@ void ShadeBehaviour::onGroupCommand(somfy_commands cmd, uint8_t repeat, uint32_t
         this->applySensorMove(this->sensors.onSunFlag(isSunny, isWindy));
         this->events.onSaveWanted();
         this->emitState();
+        this->events.onSensorFlags();
       }
       else
         ESP_LOGW(TAG, "Shade does not have sensor %d", joinShadeFlags(this->settings, false, this->s.stateFlags));
diff --git a/test/test_shadebehaviour/test_shadebehaviour.cpp b/test/test_shadebehaviour/test_shadebehaviour.cpp
index cf4cba8..f8f1fef 100644
--- a/test/test_shadebehaviour/test_shadebehaviour.cpp
+++ b/test/test_shadebehaviour/test_shadebehaviour.cpp
@@ -522,9 +522,11 @@ static void test_group_sun_flag_needs_a_sensor() {
   r.b.onGroupCommand(somfy_commands::SunFlag, 1, r.now);
   TEST_ASSERT_TRUE(r.st().stateFlags & static_cast<uint8_t>(somfy_flags_t::SunFlag));
   TEST_ASSERT_EQUAL(1, r.events.saves);
-  // today: unlike the frame rule, the group rule doesn't ask for the group
-  // flags to be worked out again; SomfyGroup does that for its own group.
-  TEST_ASSERT_EQUAL(0, r.events.sensorFlags);
+  // As for a frame, every group works its flags out again.
+  TEST_ASSERT_EQUAL(1, r.events.sensorFlags);
+  r.b.onGroupCommand(somfy_commands::Flag, 1, r.now);
+  TEST_ASSERT_FALSE(r.st().stateFlags & static_cast<uint8_t>(somfy_flags_t::SunFlag));
+  TEST_ASSERT_EQUAL(2, r.events.sensorFlags);
 }
 
 /*********************************************************************