diff --git a/Modules/posixmodule.c b/Modules/posixmodule.c
index a7a7ddd..f3d951a 100644
--- a/Modules/posixmodule.c
+++ b/Modules/posixmodule.c
@@ -2118,9 +2118,9 @@
 #endif
 
 #ifdef HAVE_GETPGID
-static char posix_getpgid__doc__[] =
+PyDoc_STRVAR(posix_getpgid__doc__,
 "getpgid(pid) -> pgid\n\
-Call the system call getpgid().";
+Call the system call getpgid().");
 
 static PyObject *
 posix_getpgid(PyObject *self, PyObject *args)