diff --git a/Marlin/boards.h b/Marlin/boards.h
index a7aceff081..18912cedab 100644
--- a/Marlin/boards.h
+++ b/Marlin/boards.h
@@ -156,6 +156,6 @@
 #define BOARD_TEENSY2           84    // Teensy++2.0 (AT90USB1286) - CLI compile: HARDWARE_MOTHERBOARD=84  make
 #define BOARD_5DPRINT           88    // 5DPrint D8 Driver Board
 
-#define MB(board) (MOTHERBOARD==BOARD_##board)
+#define MB(board) (defined(BOARD_##board) && MOTHERBOARD==BOARD_##board)
 
 #endif // __BOARDS_H