diff --git a/setup.py b/setup.py
index 9870af84..7b94d0d8 100644
--- a/setup.py
+++ b/setup.py
@@ -301,6 +301,8 @@ class psycopg_build_ext(build_ext):
             except AttributeError:
                 ext_path = os.path.join(self.build_lib,
                         'psycopg2', '_psycopg.pyd')
+            # Make sure spawn() will work if compile() was never
+            # called. https://github.com/psycopg/psycopg2/issues/380
             if not self.compiler.initialized:
                 self.compiler.initialize()
             self.compiler.spawn(