diff --git a/make_scripts_riscv/project.mk b/make_scripts_riscv/project.mk
index 66c41c7b..0d078bb4 100644
--- a/make_scripts_riscv/project.mk
+++ b/make_scripts_riscv/project.mk
@@ -183,11 +183,16 @@ export COMPONENT_INCLUDES
 include $(BL60X_SDK_PATH)/make_scripts_riscv/common.mk
 include $(BL60X_SDK_PATH)/make_scripts_riscv/toolchain.mk
 
+# In this recipe, "pip install" may need to build native code, so make sure it
+# doesn't use the cross-compilation environment. The specific list of variables
+# unset is taken from the intersection of what we export and what Python's
+# distutils uses (see CPython's Lib/distutils/sysconfig.py).
 all:
 ifeq ("$(OS)","Windows_NT")
 else
 ifeq ("$(CONFIG_CHIP_NAME)", "BL602")
-	@cd $(BL60X_SDK_PATH)/image_conf && python3 -m pip install -r requirements.txt && python3 flash_build.py $(PROJECT_NAME) $(CONFIG_CHIP_NAME)
+	@env -u CC -u CXX -u AR -u CFLAGS -u CPPFLAGS python3 -m pip install -r $(BL60X_SDK_PATH)/image_conf/requirements.txt
+	@cd $(BL60X_SDK_PATH)/image_conf && python3 flash_build.py $(PROJECT_NAME) $(CONFIG_CHIP_NAME)
 endif
 endif
 	@echo "Building Finish. To flash build output."