diff --git a/plugins/Kaleidoscope-MouseKeys/src/kaleidoscope/plugin/MouseKeys/MouseKeyDefs.h b/plugins/Kaleidoscope-MouseKeys/src/kaleidoscope/plugin/MouseKeys/MouseKeyDefs.h
index f35aa4ba..46ac2c88 100644
--- a/plugins/Kaleidoscope-MouseKeys/src/kaleidoscope/plugin/MouseKeys/MouseKeyDefs.h
+++ b/plugins/Kaleidoscope-MouseKeys/src/kaleidoscope/plugin/MouseKeys/MouseKeyDefs.h
@@ -19,11 +19,6 @@
 #define IS_MOUSE_KEY             0b00010000
 
 // Synthetic, not internal
-#define KEY_MOUSE_BTN_L MOUSE_LEFT // Synthetic key
-#define KEY_MOUSE_BTN_M MOUSE_MIDDLE  // Synthetic key
-#define KEY_MOUSE_BTN_R MOUSE_RIGHT  // Synthetic key
-#define KEY_MOUSE_BTN_P MOUSE_PREV
-#define KEY_MOUSE_BTN_N MOUSE_NEXT
 
 #define KEY_MOUSE_UP            0b0000001
 #define KEY_MOUSE_DOWN          0b0000010
@@ -60,8 +55,31 @@
 #define Key_mouseScrollDn Key(KEY_MOUSE_WHEEL | KEY_MOUSE_DOWN, KEY_FLAGS|SYNTHETIC|IS_MOUSE_KEY)
 #define Key_mouseScrollL  Key(KEY_MOUSE_WHEEL | KEY_MOUSE_LEFT, KEY_FLAGS|SYNTHETIC|IS_MOUSE_KEY)
 #define Key_mouseScrollR  Key(KEY_MOUSE_WHEEL | KEY_MOUSE_RIGHT, KEY_FLAGS|SYNTHETIC|IS_MOUSE_KEY)
+
+
+// The MOUSE_xxx button definitions come from our HID driver
+// If the HID driver doesn't define them, don't blow up compilation
+
+#ifdef MOUSE_LEFT
+
+#define KEY_MOUSE_BTN_L MOUSE_LEFT // Synthetic key
+#define KEY_MOUSE_BTN_M MOUSE_MIDDLE  // Synthetic key
+#define KEY_MOUSE_BTN_R MOUSE_RIGHT  // Synthetic key
+#define KEY_MOUSE_BTN_P MOUSE_PREV
+#define KEY_MOUSE_BTN_N MOUSE_NEXT
 #define Key_mouseBtnL     Key(KEY_MOUSE_BUTTON | KEY_MOUSE_BTN_L, KEY_FLAGS | SYNTHETIC | IS_MOUSE_KEY)
 #define Key_mouseBtnM     Key(KEY_MOUSE_BUTTON | KEY_MOUSE_BTN_M, KEY_FLAGS | SYNTHETIC | IS_MOUSE_KEY)
 #define Key_mouseBtnR     Key(KEY_MOUSE_BUTTON | KEY_MOUSE_BTN_R, KEY_FLAGS | SYNTHETIC | IS_MOUSE_KEY)
 #define Key_mouseBtnP     Key(KEY_MOUSE_BUTTON | KEY_MOUSE_BTN_P, KEY_FLAGS | SYNTHETIC | IS_MOUSE_KEY)
 #define Key_mouseBtnN     Key(KEY_MOUSE_BUTTON | KEY_MOUSE_BTN_N, KEY_FLAGS | SYNTHETIC | IS_MOUSE_KEY)
+
+#else
+
+#define Key_mouseBtnL XXX
+#define Key_mouseBtnM XXX
+#define Key_mouseBtnR XXX
+#define Key_mouseBtnP XXX
+#define Key_mouseBtnN XXX
+
+
+#endif