diff --git a/sumpy/e2e.py b/sumpy/e2e.py
index 74b3edd92d55f36bb3bb1a70559cade19aa52fd3..2d13ba5aa158e1980c47fbe7d292fa4668915887 100644
--- a/sumpy/e2e.py
+++ b/sumpy/e2e.py
@@ -745,7 +745,7 @@ class M2LPreprocessMultipole(E2EBase):
                 """],
                 [
                     lp.ValueArg("nsrc_boxes", np.int32),
-                    lp.ValueArg("src_rscale", lp.auto),
+                    lp.ValueArg("src_rscale", None),
                     lp.GlobalArg("src_expansions", None,
                         shape=("nsrc_boxes", nsrc_coeffs), offset=lp.auto),
                     lp.GlobalArg("preprocessed_src_expansions", None,