diff --git a/Objects/floatobject.c b/Objects/floatobject.c
index 8c08866..3f9bbde 100644
--- a/Objects/floatobject.c
+++ b/Objects/floatobject.c
@@ -1726,7 +1726,8 @@
     case ieee_big_endian_format:
         return PyUnicode_FromString("IEEE, big-endian");
     default:
-        Py_FatalError("insane float_format or double_format");
+        PyErr_SetString(PyExc_RuntimeError,
+                        "insane float_format or double_format");
         return NULL;
     }
 }