diff --git a/cast_test.go b/cast_test.go
index 6bea164..2282098 100644
--- a/cast_test.go
+++ b/cast_test.go
@@ -111,6 +111,12 @@ func TestToUintE(t *testing.T) {
 func TestToUint64E(t *testing.T) {
 	tests := createNumberTestSteps(uint64(0), uint64(1), uint64(8), uint64(0), uint64(8), uint64(8))
 
+	// Maximum value of uint64
+	tests = append(tests,
+		testStep{"18446744073709551615", uint64(18446744073709551615), false},
+		testStep{"18446744073709551616", uint64(0), true},
+	)
+
 	runNumberTest(
 		qt.New(t),
 		tests,
diff --git a/caste.go b/caste.go
index cd9c048..4181a2e 100644
--- a/caste.go
+++ b/caste.go
@@ -613,12 +613,12 @@ func ToUint64E(i interface{}) (uint64, error) {
 
 	switch s := i.(type) {
 	case string:
-		v, err := strconv.ParseInt(trimZeroDecimal(s), 0, 0)
+		v, err := strconv.ParseUint(trimZeroDecimal(s), 0, 0)
 		if err == nil {
 			if v < 0 {
 				return 0, errNegativeNotAllowed
 			}
-			return uint64(v), nil
+			return v, nil
 		}
 		return 0, fmt.Errorf("unable to cast %#v of type %T to uint64", i, i)
 	case json.Number: