diff --git a/src/lib/platform/EiKeyState.cpp b/src/lib/platform/EiKeyState.cpp
index 1d9dcb5dc..69bf61c40 100644
--- a/src/lib/platform/EiKeyState.cpp
+++ b/src/lib/platform/EiKeyState.cpp
@@ -345,6 +345,20 @@ void EiKeyState::updateXkbState(uint32_t keyval, bool isPressed)
   xkb_state_update_key(m_xkbState, keyval, isPressed ? XKB_KEY_DOWN : XKB_KEY_UP);
 }
 
+void EiKeyState::updateLockedModifiers(xkb_mod_mask_t lockedMods)
+{
+  // The compositor's lock state (Caps/Num/Scroll Lock) is authoritative; it
+  // also covers locks toggled while we weren't seeing the key events.
+  const auto depressedMods = xkb_state_serialize_mods(m_xkbState, XKB_STATE_MODS_DEPRESSED);
+  const auto latchedMods = xkb_state_serialize_mods(m_xkbState, XKB_STATE_MODS_LATCHED);
+  const auto depressedLayout = xkb_state_serialize_layout(m_xkbState, XKB_STATE_LAYOUT_DEPRESSED);
+  const auto latchedLayout = xkb_state_serialize_layout(m_xkbState, XKB_STATE_LAYOUT_LATCHED);
+  const auto lockedLayout = xkb_state_serialize_layout(m_xkbState, XKB_STATE_LAYOUT_LOCKED);
+  xkb_state_update_mask(
+      m_xkbState, depressedMods, latchedMods, lockedMods, depressedLayout, latchedLayout, lockedLayout
+  );
+}
+
 void EiKeyState::clearStaleModifiers()
 {
   const auto lockedMods = xkb_state_serialize_mods(m_xkbState, XKB_STATE_MODS_LOCKED);
diff --git a/src/lib/platform/EiKeyState.h b/src/lib/platform/EiKeyState.h
index aa4005fb8..8f4b941da 100644
--- a/src/lib/platform/EiKeyState.h
+++ b/src/lib/platform/EiKeyState.h
@@ -35,6 +35,7 @@ public:
   void pollPressedKeys(KeyButtonSet &pressedKeys) const override;
   KeyID mapKeyFromKeyval(std::uint32_t keyval) const;
   void updateXkbState(std::uint32_t keyval, bool isPressed);
+  void updateLockedModifiers(xkb_mod_mask_t lockedMods);
   void clearStaleModifiers() override;
 
 protected:
diff --git a/src/lib/platform/EiScreen.cpp b/src/lib/platform/EiScreen.cpp
index 7e66daa13..3c423afa8 100644
--- a/src/lib/platform/EiScreen.cpp
+++ b/src/lib/platform/EiScreen.cpp
@@ -1025,7 +1025,8 @@ void EiScreen::handleSystemEvent(const Event &)
       }
       break;
     case EI_EVENT_KEYBOARD_MODIFIERS:
-      // FIXME
+      LOG_VERBOSE("event: keyboard modifiers locked=0x%x", ei_event_keyboard_get_xkb_mods_locked(event));
+      m_keyState->updateLockedModifiers(ei_event_keyboard_get_xkb_mods_locked(event));
       break;
 
     // events below are for a receiver context (barriers)
diff --git a/src/unittests/platform/EiKeyStateTests.cpp b/src/unittests/platform/EiKeyStateTests.cpp
index a58635669..fadb17fe3 100644
--- a/src/unittests/platform/EiKeyStateTests.cpp
+++ b/src/unittests/platform/EiKeyStateTests.cpp
@@ -102,4 +102,36 @@ void EiKeyStateTests::clearStaleModifiers_shiftDownAndNumLockOn_shiftClearedAndN
   QVERIFY((keyState.pollActiveModifiers() & KeyModifierNumLock) != 0);
 }
 
+void EiKeyStateTests::updateLockedModifiers_compositorLockState_numLockFollowsCompositor()
+{
+  // Real modifier Mod2 is index 4 (Shift, Lock, Control, Mod1, Mod2, ...).
+  constexpr std::uint32_t xkbMod2Mask = 1 << 4;
+
+  TestAppUtil appUtil;
+  EventQueue eventQueue;
+  deskflow::EiKeyState keyState(nullptr, &eventQueue);
+
+  QTemporaryFile keymapFile;
+  QVERIFY(keymapFile.open());
+  const QByteArray keymapData = QByteArray::fromRawData(TestKeymap, sizeof(TestKeymap) - 1);
+  QCOMPARE(keymapFile.write(keymapData), keymapData.size());
+  QVERIFY(keymapFile.flush());
+  keyState.init(keymapFile.handle(), keymapFile.size());
+
+  keyState.updateXkbState(LeftShiftKeycode, true);
+  QVERIFY((keyState.pollActiveModifiers() & KeyModifierNumLock) == 0);
+
+  // NumLock toggled on locally, reported by the compositor
+  keyState.updateLockedModifiers(xkbMod2Mask);
+  QVERIFY((keyState.pollActiveModifiers() & KeyModifierNumLock) != 0);
+  QVERIFY((keyState.pollActiveModifiers() & KeyModifierShift) != 0);
+
+  keyState.clearStaleModifiers();
+  QVERIFY((keyState.pollActiveModifiers() & KeyModifierNumLock) != 0);
+
+  // NumLock toggled off locally
+  keyState.updateLockedModifiers(0);
+  QVERIFY((keyState.pollActiveModifiers() & KeyModifierNumLock) == 0);
+}
+
 QTEST_MAIN(EiKeyStateTests)
diff --git a/src/unittests/platform/EiKeyStateTests.h b/src/unittests/platform/EiKeyStateTests.h
index 76b2756d8..8228a554b 100644
--- a/src/unittests/platform/EiKeyStateTests.h
+++ b/src/unittests/platform/EiKeyStateTests.h
@@ -18,6 +18,7 @@ class EiKeyStateTests : public QObject
 private Q_SLOTS:
   void initTestCase();
   void clearStaleModifiers_shiftDownAndNumLockOn_shiftClearedAndNumLockPreserved();
+  void updateLockedModifiers_compositorLockState_numLockFollowsCompositor();
 
 private:
   Arch m_arch;