diff --git a/ports/rp2/Makefile b/ports/rp2/Makefile
index b6e885216..f950bc7b9 100644
--- a/ports/rp2/Makefile
+++ b/ports/rp2/Makefile
@@ -30,7 +30,7 @@ endif
 
 $(VERBOSE)MAKESILENT = -s
 
-CMAKE_ARGS = -DMICROPY_BOARD=$(BOARD) -DMICROPY_BOARD_DIR="$(abspath $(BOARD_DIR))"
+CMAKE_ARGS += -DMICROPY_BOARD=$(BOARD) -DMICROPY_BOARD_DIR="$(abspath $(BOARD_DIR))"
 
 ifdef USER_C_MODULES
 CMAKE_ARGS += -DUSER_C_MODULES=${USER_C_MODULES}