diff --git a/cpf/lib.go b/cpf/lib.go
index c58828f..60ee8a6 100644
--- a/cpf/lib.go
+++ b/cpf/lib.go
@@ -39,8 +39,12 @@ func Check(s string) bool {
 		d1 = d1 + (v * mul)
 		mul--
 	}
-	mod1 := (d1 * 10) % 11
-
+	mod1 := (d1) % 11
+	if mod1 < 2 {
+		mod1 = 0
+	} else {
+		mod1 = 11 - mod1
+	}
 	d2 := 0
 	mul = 11
 	for _, v := range nums[0 : len(nums)-2] {
@@ -49,6 +53,11 @@ func Check(s string) bool {
 	}
 	d2 = d2 + (mod1 * mul)
 
-	mod2 := (d2 * 10) % 11
+	mod2 := (d2) % 11
+	if mod2 < 2 {
+		mod2 = 0
+	} else {
+		mod2 = 11 - mod2
+	}
 	return mod1 == nums[len(nums)-2] && mod2 == nums[len(nums)-1]
 }
diff --git a/cpf/lib_test.go b/cpf/lib_test.go
index aa0b4dc..5d2a008 100644
--- a/cpf/lib_test.go
+++ b/cpf/lib_test.go
@@ -15,6 +15,8 @@ func TestCheck(t *testing.T) {
 		"377.100.400-46",
 		"845.846.910-37",
 		"845.846.910-17",
+		"39412818602",
+		"768.974.608-00",
 	} {
 		ret := Check(v)
 		log.Printf("%s=>%v", v, ret)