diff --git a/ports/unix/Makefile b/ports/unix/Makefile
index d2af8b0871..0ff2e4b6e8 100644
--- a/ports/unix/Makefile
+++ b/ports/unix/Makefile
@@ -27,8 +27,8 @@ FROZEN_MANIFEST ?= variants/manifest.py
 PROG ?= micropython
 
 # qstr definitions (must come before including py.mk)
-QSTR_DEFS = qstrdefsport.h
-QSTR_GLOBAL_DEPENDENCIES = $(VARIANT_DIR)/mpconfigvariant.h
+QSTR_DEFS += qstrdefsport.h
+QSTR_GLOBAL_DEPENDENCIES += $(VARIANT_DIR)/mpconfigvariant.h
 
 # OS name, for simple autoconfig
 UNAME_S := $(shell uname -s)