Fix typo in error checking spotted by Just...
diff --git a/Objects/fileobject.c b/Objects/fileobject.c
index 257702f..1d85e20 100644
--- a/Objects/fileobject.c
+++ b/Objects/fileobject.c
@@ -982,7 +982,7 @@
 		return -1;
 	}
 	args = Py_BuildValue("(O)", value);
-	if (value == NULL) {
+	if (args == NULL) {
 		Py_DECREF(value);
 		Py_DECREF(writer);
 		return -1;