diff --git a/keyboards/gmmk/gmmk3/p100/iso/keymaps/viach/keymap.c b/keyboards/gmmk/gmmk3/p100/iso/keymaps/viach/keymap.c
index cac10312e5b..011b6371a32 100644
--- a/keyboards/gmmk/gmmk3/p100/iso/keymaps/viach/keymap.c
+++ b/keyboards/gmmk/gmmk3/p100/iso/keymaps/viach/keymap.c
@@ -41,6 +41,7 @@ enum custom_layers {
     WIN_FL,    // Windows Function Layer
     MACOS_BL,  // Mac OS Base Layer
     MACOS_FL   // Mac OS Function Layer
+    _CL        // Custom Layer
 };
 
 const uint16_t PROGMEM keymaps[][MATRIX_ROWS][MATRIX_COLS] = {
@@ -87,6 +88,17 @@ const uint16_t PROGMEM keymaps[][MATRIX_ROWS][MATRIX_COLS] = {
         _______,  _______,  RGB_SAD,  RGB_SAI,  RGB_SPD,  RGB_SPI,  _______,  _______,  _______,  _______,  _______,  _______,            _______,               RGB_VAI,               _______,  _______,  _______,  _______,
         _______,  _______,  _______,                                _______,                                _______,  _______,  _______,  _______,     RGB_RMOD, RGB_VAD,  RGB_MOD,     _______,            _______
     ),
+
+    /* Custom Layer */
+    [_CL] = LAYOUT(
+        _______,            _______,  _______,  _______,  _______,  _______,  _______,  _______,  _______,  _______,  _______,  _______,  _______,     _______,  _______,  _______,                                   _______,
+
+        _______,  _______,  _______,  _______,  _______,  _______,  _______,  _______,  _______,  _______,  _______,  _______,  _______,  _______,     _______,  _______,  _______,     _______,  _______,  _______,  _______,
+        _______,  _______,  _______,  _______,  _______,  _______,  _______,  _______,  _______,  _______,  _______,  _______,  _______,  _______,     _______,  _______,  _______,     _______,  _______,  _______,  _______,
+        _______,  _______,  _______,  _______,  _______,  _______,  _______,  _______,  _______,  _______,  _______,  _______,            _______,                                      _______,  _______,  _______,
+        _______,            _______,  _______,  _______,  _______,  _______,  _______,  _______,  _______,  _______,  _______,            _______,               _______,               _______,  _______,  _______,  _______,
+        _______,  _______,  _______,                                _______,                                _______,  _______,  _______,  _______,     _______,  _______,  _______,     _______,            _______
+    )
 };
  
 #if defined(ENCODER_MAP_ENABLE)