diff --git a/either/either.go b/either/either.go
index 006b301..992ef6d 100644
--- a/either/either.go
+++ b/either/either.go
@@ -33,7 +33,7 @@ func Of[E, A any](value A) Either[E, A] {
 	return F.Pipe1(value, Right[E, A])
 }
 
-func FromIO[E, IO ~func() A, A any](f IO) Either[E, A] {
+func FromIO[E any, IO ~func() A, A any](f IO) Either[E, A] {
 	return F.Pipe1(f(), Right[E, A])
 }
 
diff --git a/either/either_test.go b/either/either_test.go
index a413598..7f50a21 100644
--- a/either/either_test.go
+++ b/either/either_test.go
@@ -71,7 +71,6 @@ func TestReduce(t *testing.T) {
 	assert.Equal(t, "foo", F.Pipe1(Left[string, string]("bar"), Reduce[string](s.Concat, "foo")))
 
 }
-
 func TestAp(t *testing.T) {
 	f := S.Size
 
@@ -120,3 +119,10 @@ func TestStringer(t *testing.T) {
 	var s fmt.Stringer = e
 	assert.Equal(t, exp, s.String())
 }
+
+func TestFromIO(t *testing.T) {
+	f := func() string { return "abc" }
+	e := FromIO[error](f)
+
+	assert.Equal(t, Right[error]("abc"), e)
+}