diff --git a/src/openultrasast/cpg/queries/census.sc b/src/openultrasast/cpg/queries/census.sc
index e8b22ee..dc190ed 100644
--- a/src/openultrasast/cpg/queries/census.sc
+++ b/src/openultrasast/cpg/queries/census.sc
@@ -23,7 +23,7 @@
       ujson.Obj(
         "files"     -> cpg.file.size.toString,
         "methods"   -> cpg.method.size.toString,
-        "overlays"  -> cpg.metaData.overlays.l.flatten.mkString(","),
+        "overlays"  -> cpg.metaData.overlays.l.mkString(","),
         "maxHeapMB" -> (Runtime.getRuntime.maxMemory / 1048576).toString
       )
     )
diff --git a/tests/test_cpg_queries_compile.py b/tests/test_cpg_queries_compile.py
index 9b5646d..5da68eb 100644
--- a/tests/test_cpg_queries_compile.py
+++ b/tests/test_cpg_queries_compile.py
@@ -56,4 +56,12 @@ def test_each_query_compiles_and_answers(name: str, tmp_path: Path) -> None:
     done = subprocess.run(command, capture_output=True, text=True, timeout=900, check=False, cwd=str(tmp_path))
 
     assert done.returncode == 0, f"{name}.sc did not run: {(done.stderr or done.stdout or '')[-500:]}"
-    assert extract_payload(done.stdout or "") is not None, f"{name}.sc produced no parseable payload"
+    payload = extract_payload(done.stdout or "")
+    assert payload is not None, f"{name}.sc produced no parseable payload"
+    if name == "census":
+        # The overlay list is what the backend checks for the dataflow layer. It shipped once as a list of
+        # CHARACTERS (`b,a,s,e,...`) -- one `flatten` too many -- and every real build warned that its graph
+        # lacked `dataflowOss` while carrying it. `importCpg` applies the layer here, so it must be named.
+        overlays = str(payload.get("overlays", "")).split(",")
+        assert "dataflowOss" in overlays, f"census reports overlays {overlays!r}, which is not a list of layer names"
+        assert str(payload.get("maxHeapMB", "")).isdigit()