diff --git a/denops/tataku/load.ts b/denops/tataku/load.ts
index e2fe1dc..8c658ba 100644
--- a/denops/tataku/load.ts
+++ b/denops/tataku/load.ts
@@ -13,7 +13,7 @@ type Query = {
   name: string;
 };
 
-type Factory<T> = (denops: Denops, options: unknown) => T;
+type Factory<T> = (denops: Denops, options: unknown) => T | Promise<T>;
 
 function search(
   denops: Denops,
@@ -91,7 +91,7 @@ export function loadProcessor(
     .andThen((path) => {
       return ResultAsync.fromPromise(
         import(path.href).then((e) => e.default),
-        (cause) => new Error(`Failed to processor-${name}`, { cause }),
+        (cause) => new Error(`Failed to load processor-${name}`, { cause }),
       );
     })
     .andThen((factory: unknown) => {
@@ -110,7 +110,7 @@ export function loadEmitter(
     .andThen((path) => {
       return ResultAsync.fromPromise(
         import(path.href).then((e) => e.default),
-        (cause) => new Error(`Failed to emitter-${name}`, { cause }),
+        (cause) => new Error(`Failed to load emitter-${name}`, { cause }),
       );
     })
     .andThen((factory: unknown) => {
diff --git a/denops/tataku/tataku.ts b/denops/tataku/tataku.ts
index 1b00074..9c06a55 100644
--- a/denops/tataku/tataku.ts
+++ b/denops/tataku/tataku.ts
@@ -8,6 +8,7 @@ import {
   validate,
 } from "./types.ts";
 import { loadCollector, loadEmitter, loadProcessor } from "./load.ts";
+import { convertError } from "./utils.ts";
 
 type Streams = {
   collector: Collector;
@@ -42,19 +43,29 @@ export function prepareStreams(
       ResultAsync.combine([
         loadCollector(denops, recipe.collector.name)
           .andThen((factory) =>
-            okAsync(factory(denops, recipe.collector.options ?? {}))
+            ResultAsync.fromPromise(
+              Promise.resolve(factory(denops, recipe.collector.options ?? {})),
+              convertError("Failed to load collector"),
+            )
           ),
         ResultAsync.combine(
           recipe.processor.map((page) =>
             loadProcessor(denops, page.name)
               .andThen((factory) =>
-                okAsync(factory(denops, page.options ?? {}))
+                ResultAsync.fromPromise(
+                  Promise.resolve(factory(denops, page.options ?? {})),
+                  convertError("Failed to load processor"),
+                )
               )
           ),
-        ).andThen((streams) => okAsync(new CombinedProcessorStream(streams))),
+        )
+          .andThen((streams) => okAsync(new CombinedProcessorStream(streams))),
         loadEmitter(denops, recipe.emitter.name)
           .andThen((factory) =>
-            okAsync(factory(denops, recipe.emitter.options ?? {}))
+            ResultAsync.fromPromise(
+              Promise.resolve(factory(denops, recipe.emitter.options ?? {})),
+              convertError("Failed to load emitter"),
+            )
           ),
       ])
     )
diff --git a/denops/tataku/utils.ts b/denops/tataku/utils.ts
index a0a1dee..8fbd91e 100644
--- a/denops/tataku/utils.ts
+++ b/denops/tataku/utils.ts
@@ -35,3 +35,19 @@ export async function handleError(
     );
   }
 }
+
+/**
+ * Convert some value to Error
+ *
+ * @param cause Some error thing
+ * @param message The message of error if using cause is not Error
+ * @returns Converted error
+ */
+export function convertError(message = "Failed"): (e: unknown) => Error {
+  return (cause) => {
+    if (cause instanceof Error) {
+      return cause;
+    }
+    return new Error(message, { cause });
+  };
+}