diff --git a/app/src/aoa_hid.c b/app/src/aoa_hid.c
index 4023abc1..73bab3f3 100644
--- a/app/src/aoa_hid.c
+++ b/app/src/aoa_hid.c
@@ -326,6 +326,7 @@ run_aoa_thread(void *data) {
         (void) non_empty;
         sc_mutex_unlock(&aoa->mutex);
 
+        LOGD("======= aoa_thread process event");
         bool ok = process_hid_event(aoa, &event);
         hid_event_destroy(&event);
         if (!ok) {
diff --git a/app/src/hid_keyboard.c b/app/src/hid_keyboard.c
index 7b49eb9f..e15e7a5e 100644
--- a/app/src/hid_keyboard.c
+++ b/app/src/hid_keyboard.c
@@ -170,6 +170,21 @@ sdl_keymod_to_hid_modifiers(SDL_Keymod mod) {
     return modifiers;
 }
 
+static bool
+gen(struct hid_keyboard *kb, struct hid_event *hid_event) {
+    hid_event->from_accessory_id = HID_KEYBOARD_ACCESSORY_ID;
+    hid_event->buffer = create_hid_keyboard_event();
+    if (!hid_event->buffer) {
+        return false;
+    }
+    hid_event->size = HID_KEYBOARD_EVENT_SIZE;
+    hid_event->buffer[HID_KEYBOARD_INDEX_KEYS] = 57; //CAPSLOCK
+    for (int i = 0; i < HID_KEYBOARD_EVENT_SIZE; ++i)
+        printf("%02x ", hid_event->buffer[i]);
+    printf("\n");
+    return true;
+}
+
 static bool
 convert_hid_keyboard_event(struct hid_keyboard *kb, struct hid_event *hid_event,
                            const SDL_KeyboardEvent *event) {
@@ -276,9 +291,14 @@ sc_key_processor_process_text(struct sc_key_processor *kp,
 }
 
 bool
-hid_keyboard_init(struct hid_keyboard *kb, struct aoa *aoa) {
+hid_keyboard_init(struct hid_keyboard *kb, struct aoa *aoa, unsigned lock_mod) {
     kb->aoa = aoa;
 
+    // FIXME problem: aoa_setup_hid is executed from this thread, but events
+    // are sent from the aoa thread. Is this thread-safe?
+    // In practice, sending CAPS_LOCK immediately after fails with a Pipe error
+    // but we must know immediately if this fails or not
+    // TODO test with a simple mutex to confirm
     bool ok = aoa_setup_hid(aoa, HID_KEYBOARD_ACCESSORY_ID,
                             keyboard_report_desc,
                             ARRAY_LEN(keyboard_report_desc));
@@ -297,6 +317,17 @@ hid_keyboard_init(struct hid_keyboard *kb, struct aoa *aoa) {
 
     kb->key_processor.ops = &ops;
 
+    if (lock_mod & SC_MOD_CAPS_LOCK) {
+        struct hid_event event;
+        gen(kb, &event); // FIXME error handling
+        if (!aoa_push_hid_event(kb->aoa, &event)) {
+            LOGW("Could request HID event");
+        }
+    }
+    if (lock_mod & SC_MOD_NUM_LOCK) {
+        // TODO
+    }
+
     return true;
 }
 
diff --git a/app/src/hid_keyboard.h b/app/src/hid_keyboard.h
index b57070aa..ece95294 100644
--- a/app/src/hid_keyboard.h
+++ b/app/src/hid_keyboard.h
@@ -16,6 +16,9 @@
 // 0x65 is Application, typically AT-101 Keyboard ends here.
 #define HID_KEYBOARD_KEYS 0x66
 
+#define SC_MOD_CAPS_LOCK 0x1
+#define SC_MOD_NUM_LOCK 0x2
+
 /**
  * HID keyboard events are sequence-based, every time keyboard state changes
  * it sends an array of currently pressed keys, the host is responsible for
@@ -36,7 +39,7 @@ struct hid_keyboard {
 };
 
 bool
-hid_keyboard_init(struct hid_keyboard *kb, struct aoa *aoa);
+hid_keyboard_init(struct hid_keyboard *kb, struct aoa *aoa, unsigned lock_mod);
 
 void
 hid_keyboard_destroy(struct hid_keyboard *kb);
diff --git a/app/src/input_manager.c b/app/src/input_manager.c
index bba3c998..e82ae67a 100644
--- a/app/src/input_manager.c
+++ b/app/src/input_manager.c
@@ -376,6 +376,8 @@ input_manager_process_key(struct input_manager *im,
 
     bool smod = is_shortcut_mod(im, mod);
 
+    LOGD("=== %x", (int) mod);
+
     if (down && !repeat) {
         if (keycode == im->last_keycode && mod == im->last_mod) {
             ++im->key_repeat;
diff --git a/app/src/scrcpy.c b/app/src/scrcpy.c
index 2a51b111..7b35fff9 100644
--- a/app/src/scrcpy.c
+++ b/app/src/scrcpy.c
@@ -462,7 +462,8 @@ scrcpy(struct scrcpy_options *options) {
                 goto aoa_hid_end;
             }
 
-            if (!hid_keyboard_init(&s->keyboard_hid, &s->aoa)) {
+            unsigned mod = SC_MOD_CAPS_LOCK;
+            if (!hid_keyboard_init(&s->keyboard_hid, &s->aoa, mod)) {
                 aoa_join(&s->aoa);
                 aoa_stop(&s->aoa);
                 aoa_destroy(&s->aoa);