--- ./Modules/mathmodule.c_orig	2021-02-01 08:36:07.226428203 -0600
+++ ./Modules/mathmodule.c	2021-02-01 08:39:17.666403170 -0600
@@ -3391,6 +3391,12 @@
            Bug fixed in bos.adt.libm 7.2.2.0 by APAR IV95512. */
         return PyFloat_FromDouble(y);
     }
+    if (Py_IS_NAN(x)) {
+        return PyFloat_FromDouble(x);
+    }
+    if (Py_IS_NAN(y)) {
+        return PyFloat_FromDouble(y);
+    }
 #endif
     return PyFloat_FromDouble(nextafter(x, y));
 }