diff --git a/setup.py b/setup.py
index 8eb0b3c6b33..68d2d6b55be 100755
--- a/setup.py
+++ b/setup.py
@@ -330,8 +330,8 @@ def build_extensions(self):
             _add_directory(library_dirs, lib_root)
             _add_directory(include_dirs, include_root)
 
-        # respect CFLAGS/LDFLAGS
-        for k in ('CFLAGS', 'LDFLAGS'):
+        # respect CFLAGS/CPPFLAGS/LDFLAGS
+        for k in ('CFLAGS', 'CPPFLAGS', 'LDFLAGS'):
             if k in os.environ:
                 for match in re.finditer(r'-I([^\s]+)', os.environ[k]):
                     _add_directory(include_dirs, match.group(1))