diff --git a/py/mkenv.mk b/py/mkenv.mk
index 4bc71edd78..b8dde807e8 100644
--- a/py/mkenv.mk
+++ b/py/mkenv.mk
@@ -42,14 +42,14 @@ ECHO = @echo
 CP = cp
 MKDIR = mkdir
 SED = sed
-PYTHON = python
+PYTHON ?= python
 
-AS = $(CROSS_COMPILE)as
-CC = $(CROSS_COMPILE)gcc
-LD = $(CROSS_COMPILE)ld
-OBJCOPY = $(CROSS_COMPILE)objcopy
-SIZE = $(CROSS_COMPILE)size
-STRIP = $(CROSS_COMPILE)strip
+AS ?= $(CROSS_COMPILE)as
+CC ?= $(CROSS_COMPILE)gcc
+LD ?= $(CROSS_COMPILE)ld
+OBJCOPY ?= $(CROSS_COMPILE)objcopy
+SIZE ?= $(CROSS_COMPILE)size
+STRIP ?= $(CROSS_COMPILE)strip
 
 all:
 .PHONY: all
diff --git a/py/py-version.sh b/py/py-version.sh
index 93b8d7a1fd..88c3ebb986 100755
--- a/py/py-version.sh
+++ b/py/py-version.sh
@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/bin/sh
 
 # Note: git describe doesn't work if no tag is available
 git_tag="$(git describe --dirty --always)"
diff --git a/unix/Makefile b/unix/Makefile
index ffc3391a14..485009135f 100644
--- a/unix/Makefile
+++ b/unix/Makefile
@@ -48,7 +48,10 @@ ifeq ($(MICROPY_PY_FFI),1)
 LIBFFI_LDFLAGS_MOD := $(shell pkg-config --libs libffi)
 LIBFFI_CFLAGS_MOD := $(shell pkg-config --cflags libffi)
 CFLAGS_MOD += $(LIBFFI_CFLAGS_MOD) -DMICROPY_PY_FFI=1
-LDFLAGS_MOD += -ldl $(LIBFFI_LDFLAGS_MOD)
+ifeq ($(UNAME_S),Linux)
+LDFLAGS_MOD += -ldl
+endif
+LDFLAGS_MOD += $(LIBFFI_LDFLAGS_MOD)
 SRC_MOD += modffi.c
 endif