diff --git a/autopxd/__init__.py b/autopxd/__init__.py
index 20709bf..79e502d 100644
--- a/autopxd/__init__.py
+++ b/autopxd/__init__.py
@@ -303,9 +303,11 @@ def lines(self):
 
 
 def preprocess(code, extra_cpp_args=[]):
-    proc = subprocess.Popen([
-        'cpp', '-nostdinc', '-D__attribute__(x)=', '-I', BUILTIN_HEADERS_DIR,
-    ] + extra_cpp_args + ['-'], stdin=subprocess.PIPE, stdout=subprocess.PIPE)
+    proc = subprocess.Popen(
+        ['cpp', '-nostdinc', '-D__attribute__(x)=',
+            '-I', BUILTIN_HEADERS_DIR] +
+        extra_cpp_args + ['-'],
+        stdin=subprocess.PIPE, stdout=subprocess.PIPE, universal_newlines=True)
     result = []
     result.append(proc.communicate(input=code.encode('utf-8'))[0])
     while proc.poll() is None:
@@ -328,7 +330,7 @@ def parse(code, extra_cpp_args=[]):
 
 
 def translate(code, hdrname, extra_cpp_args=[]):
-    extra_incdir = os.path.dirname(hdrname)
+    extra_incdir = os.path.normpath(os.path.dirname(hdrname))
     p = AutoPxd(hdrname)
     p.visit(parse(code, extra_cpp_args=['-I', extra_incdir]))
     return str(p)