diff --git a/src/main/scala/net/yoshinorin/qualtet/syntax/io.scala b/src/main/scala/net/yoshinorin/qualtet/syntax/io.scala
deleted file mode 100644
index 2de99bae..00000000
--- a/src/main/scala/net/yoshinorin/qualtet/syntax/io.scala
+++ /dev/null
@@ -1,17 +0,0 @@
-package net.yoshinorin.qualtet.syntax
-
-import cats.effect.IO
-import scala.reflect.ClassTag
-
-trait io {
-
-  extension [A: ClassTag](io: IO[Option[A]]) {
-    def throwIfNone[F <: Throwable](t: F): IO[A] = {
-      io.flatMap {
-        case Some(a: A) => IO(a)
-        case _ => IO.raiseError(t)
-      }
-    }
-  }
-
-}
diff --git a/src/main/scala/net/yoshinorin/qualtet/syntax/monad.scala b/src/main/scala/net/yoshinorin/qualtet/syntax/monad.scala
new file mode 100644
index 00000000..de74b6a1
--- /dev/null
+++ b/src/main/scala/net/yoshinorin/qualtet/syntax/monad.scala
@@ -0,0 +1,18 @@
+package net.yoshinorin.qualtet.syntax
+
+import cats.{Monad, MonadError}
+import scala.reflect.ClassTag
+import cats.syntax.flatMap.toFlatMapOps
+
+trait monad {
+
+  extension [F[_]: Monad, A: ClassTag](monad: F[Option[A]]) {
+    def throwIfNone[T <: Throwable](t: T)(implicit me: MonadError[F, Throwable]): F[A] = {
+      monad.flatMap {
+        case Some(a: A) => Monad[F].pure(a)
+        case _ => MonadError[F, Throwable].raiseError(t)
+      }
+    }
+  }
+
+}
diff --git a/src/main/scala/net/yoshinorin/qualtet/syntax/syntax.scala b/src/main/scala/net/yoshinorin/qualtet/syntax/syntax.scala
index 3b4f8656..a27e2f34 100644
--- a/src/main/scala/net/yoshinorin/qualtet/syntax/syntax.scala
+++ b/src/main/scala/net/yoshinorin/qualtet/syntax/syntax.scala
@@ -1,3 +1,3 @@
 package net.yoshinorin.qualtet
 
-package object syntax extends string with eitherT with tuple with validator with io with option with json with http with throwable with points
+package object syntax extends string with eitherT with tuple with validator with monad with option with json with http with throwable with points
diff --git a/src/main/scala/net/yoshinorin/qualtet/syntax/throwable.scala b/src/main/scala/net/yoshinorin/qualtet/syntax/throwable.scala
index 0472d1bd..82289423 100644
--- a/src/main/scala/net/yoshinorin/qualtet/syntax/throwable.scala
+++ b/src/main/scala/net/yoshinorin/qualtet/syntax/throwable.scala
@@ -19,4 +19,5 @@ trait throwable {
       IO(e)
     }
   }
+
 }