diff --git a/bend2/comp.ts b/bend2/comp.ts
index f2c29dad0..840ba25d0 100644
--- a/bend2/comp.ts
+++ b/bend2/comp.ts
@@ -3291,8 +3291,8 @@ function js_def(fl: File, k: Bend.Name, def: Def): void {
         js_func(fl, def.h ?? die("unelaborated def " + k), def.T, params);
       } else {
         const n = eff_name(k);
-        file_push(fl, `return { $: "$FFI", run: $0eff.${n}, need: $0eff.${n
-          }_need, args: [${params.join(", ")}], kont: ${kont[0]} };`);
+        file_push(fl, `return { $: "$FFI", run: $0eff.${n}.run, need: $0eff.${n
+          }.need, args: [${params.join(", ")}], kont: ${kont[0]} };`);
       }
     });
   file_push(fl, "");
@@ -3317,9 +3317,8 @@ export function js_lib(book: Bend.Book, roots: Bend.Name[],
     ms.push(n);
     const rows = grps.get(path) ?? [];
     grps.set(path, rows);
-    for (const m of [n, n + "_need"]) {
-      rows.push(`  ${m}: typeof ${m} === "function" ? ${m} : undefined,`);
-    }
+    rows.push(`  ["${n}"]: { run: typeof ${n} === "function" ? ${n} : undefined,`
+      + ` need: typeof ${n}_need === "function" ? ${n}_need : undefined },`);
   }
   const dup = ms.find((m, i) => ms.indexOf(m) < i);
   if (dup !== undefined) die("two names mangle to " + dup);
diff --git a/tests/io/effect_need_collision.bend b/tests/io/effect_need_collision.bend
new file mode 100644
index 000000000..1036e8d05
--- /dev/null
+++ b/tests/io/effect_need_collision.bend
@@ -0,0 +1,16 @@
+# An effect named like another module's scheduling helper keeps its value.
+import Base
+
+def A.run(ms: U32) -> IO(U32):
+  import "./effect_need_worker.js"
+
+def A.run_need() -> IO(U32):
+  import "./effect_need_name.js"
+
+def main() -> IO(Unit):
+  do IO<Unit>:
+    y : U32 <- A.run_need()
+    x : U32 <- A.run(1)
+    IO.print(U32.show(x) ++ " " ++ U32.show(y))
+
+#|11 22
diff --git a/tests/io/effect_need_collision_reverse.bend b/tests/io/effect_need_collision_reverse.bend
new file mode 100644
index 000000000..fbc63aa03
--- /dev/null
+++ b/tests/io/effect_need_collision_reverse.bend
@@ -0,0 +1,16 @@
+# Reversing discovery order also preserves the scheduling helper's call.
+import Base
+
+def A.run(ms: U32) -> IO(U32):
+  import "./effect_need_worker.js"
+
+def A.run_need() -> IO(U32):
+  import "./effect_need_name.js"
+
+def main() -> IO(Unit):
+  do IO<Unit>:
+    x : U32 <- A.run(1)
+    y : U32 <- A.run_need()
+    IO.print(U32.show(x) ++ " " ++ U32.show(y))
+
+#|11 22
diff --git a/tests/io/effect_need_name.js b/tests/io/effect_need_name.js
new file mode 100644
index 000000000..a2de7f6e6
--- /dev/null
+++ b/tests/io/effect_need_name.js
@@ -0,0 +1,3 @@
+function a_run_need() {
+  return 22;
+}
diff --git a/tests/io/effect_need_worker.js b/tests/io/effect_need_worker.js
new file mode 100644
index 000000000..969153e5b
--- /dev/null
+++ b/tests/io/effect_need_worker.js
@@ -0,0 +1,12 @@
+let asked = false;
+
+function a_run(ms) {
+  const value = asked ? 11 : 99;
+  asked = false;
+  return value;
+}
+
+function a_run_need() {
+  asked = true;
+  return { time: true };
+}
diff --git a/tests/io/effect_proto.bend b/tests/io/effect_proto.bend
new file mode 100644
index 000000000..8bd2b0d08
--- /dev/null
+++ b/tests/io/effect_proto.bend
@@ -0,0 +1,12 @@
+# The foreign table keeps __proto__ as an own effect entry.
+import Base
+
+def __proto__() -> IO(U32):
+  import "./effect_proto.js"
+
+def main() -> IO(Unit):
+  do IO<Unit>:
+    x : U32 <- __proto__()
+    IO.print(U32.show(x))
+
+#|77
diff --git a/tests/io/effect_proto.js b/tests/io/effect_proto.js
new file mode 100644
index 000000000..bb0cb6fd8
--- /dev/null
+++ b/tests/io/effect_proto.js
@@ -0,0 +1,3 @@
+function __proto__() {
+  return 77;
+}