diff --git a/setup.py b/setup.py
index 19e6bc36686..598482e50a1 100644
--- a/setup.py
+++ b/setup.py
@@ -1811,7 +1811,7 @@ class PyBuildExt(build_ext):
 
     def _decimal_ext(self):
         extra_compile_args = []
-        undef_macros=['NDEBUG']
+        undef_macros = ['NDEBUG']
         if '--with-system-libmpdec' in sysconfig.get_config_var("CONFIG_ARGS"):
             include_dirs = []
             libraries = ['mpdec']