diff --git a/loopy/preprocess.py b/loopy/preprocess.py
index bbc15c03ad38d7eb6c4046e77ecc450d2018dd3a..229c6b7caafb17c309746edefffff88019ef4f50 100644
--- a/loopy/preprocess.py
+++ b/loopy/preprocess.py
@@ -887,7 +887,7 @@ def _insert_subdomain_into_domain_tree(kernel, domains, subdomain):
 
 
 def realize_reduction(kernel, insn_id_filter=None, unknown_types_ok=True,
-                      automagic_scans_ok=True, force_scan=False,
+                      automagic_scans_ok=False, force_scan=False,
                       force_outer_iname_for_scan=None):
     """Rewrites reductions into their imperative form. With *insn_id_filter*
     specified, operate only on the instruction with an instruction id matching
diff --git a/test/test_scan.py b/test/test_scan.py
index fab7f1b0ac4ab4311ce9fc14948392a730de3af8..08754819c9a156403aba689cb3e9c238144e7905 100644
--- a/test/test_scan.py
+++ b/test/test_scan.py
@@ -121,7 +121,7 @@ def test_automatic_scan_detection():
         )
 
     cgr = lp.generate_code_v2(knl)
-    assert "scan" in cgr.device_code()
+    assert "scan" not in cgr.device_code()
 
 
 def test_selective_scan_realization():