diff --git a/docs/en/mouse_keys.md b/docs/en/mouse_keys.md
index bb749d1..d57ff0d 100644
--- a/docs/en/mouse_keys.md
+++ b/docs/en/mouse_keys.md
@@ -15,6 +15,8 @@ keyboard.modules.append(MouseKeys())
 | `KC.MB_LMB`               | Left mouse button                    |
 | `KC.MB_RMB`               | Right mouse button                   |
 | `KC.MB_MMB`               | Middle mouse button                  |
+| `KC.MB_BTN4`              | mouse button 4                       |
+| `KC.MB_BTN5`              | mouse button 5                       |
 | `KC.MW_UP`                | Mouse wheel up                       |
 | `KC.MW_DOWN`, `KC.MW_DN`  | Mouse wheel down                     |
 | `KC.MS_UP`                | Move mouse cursor up                 |
diff --git a/kmk/modules/mouse_keys.py b/kmk/modules/mouse_keys.py
index d4dd4b4..55dacab 100644
--- a/kmk/modules/mouse_keys.py
+++ b/kmk/modules/mouse_keys.py
@@ -28,6 +28,14 @@ class MouseKeys(Module):
             names=('MB_RMB',),
             code=2,
         )
+        make_mouse_key(
+            names=('MB_BTN4',),
+            code=8,
+        )
+        make_mouse_key(
+            names=('MB_BTN5',),
+            code=16,
+        )
         make_key(
             names=('MW_UP',),
             on_press=self._mw_up_press,