diff --git a/pylibfdt/Makefile.pylibfdt b/pylibfdt/Makefile.pylibfdt
index 0d8c010..3d99fd4 100644
--- a/pylibfdt/Makefile.pylibfdt
+++ b/pylibfdt/Makefile.pylibfdt
@@ -7,7 +7,8 @@ PYMODULE = $(PYLIBFDT_objdir)/_libfdt.so
 
 $(PYMODULE): $(PYLIBFDT_srcs) $(WRAP)
 	@$(VECHO) PYMOD $@
-	python $(PYLIBFDT_objdir)/setup.py "$(CPPFLAGS)" $^
+	SOURCES="$^" CPPFLAGS="$(CPPFLAGS)" \
+	python $(PYLIBFDT_objdir)/setup.py --quiet build_ext --inplace
 	mv _libfdt.so $(PYMODULE)
 
 $(WRAP): $(PYLIBFDT_srcdir)/libfdt.swig
diff --git a/pylibfdt/setup.py b/pylibfdt/setup.py
index 0ff160c..e45f110 100644
--- a/pylibfdt/setup.py
+++ b/pylibfdt/setup.py
@@ -2,6 +2,9 @@
 
 """
 setup.py file for SWIG libfdt
+
+Files to be built into the extension are provided in SOURCES
+C flags to use are provided in CPPFLAGS
 """
 
 from distutils.core import setup, Extension
@@ -9,22 +12,15 @@ import os
 import sys
 
 progname = sys.argv[0]
-cflags = sys.argv[1]
-files = sys.argv[2:]
-
-if cflags:
-    cflags = [flag for flag in cflags.split(' ') if flag]
-else:
-    cflags = None
+files = os.environ['SOURCES'].split()
+cflags = os.environ['CPPFLAGS'].split()
 
 libfdt_module = Extension(
     '_libfdt',
     sources = files,
-    extra_compile_args =  cflags
+    extra_compile_args = cflags
 )
 
-sys.argv = [progname, '--quiet', 'build_ext', '--inplace']
-
 setup (name = 'libfdt',
        version = '0.1',
        author      = "Simon Glass <sjg@chromium.org>",