diff --git a/types.go b/types.go
index 68d5adea..4b58fd91 100644
--- a/types.go
+++ b/types.go
@@ -99,7 +99,7 @@ func (n *NullString) UnmarshalJSON(b []byte) error {
 
 // UnmarshalJSON correctly deserializes a NullInt64 from JSON
 func (n *NullInt64) UnmarshalJSON(b []byte) error {
-	var s interface{}
+	var s json.Number
 	if err := json.Unmarshal(b, &s); err != nil {
 		return err
 	}
diff --git a/types_test.go b/types_test.go
index eda798bf..bbc92cd7 100644
--- a/types_test.go
+++ b/types_test.go
@@ -12,7 +12,7 @@ import (
 var (
 	filledRecord = nullTypedRecord{
 		StringVal:  NewNullString("wow"),
-		Int64Val:   NewNullInt64(42),
+		Int64Val:   NewNullInt64(1483272000),
 		Float64Val: NewNullFloat64(1.618),
 		TimeVal:    NewNullTime(time.Date(2009, 1, 3, 18, 15, 5, 0, time.UTC)),
 		BoolVal:    NewNullBool(true),
@@ -70,7 +70,7 @@ func TestNullTypesJSON(t *testing.T) {
 			in:   &filledRecord.Int64Val,
 			in2:  filledRecord.Int64Val,
 			out:  new(NullInt64),
-			want: "42",
+			want: "1483272000",
 		},
 		{
 			in:   &filledRecord.StringVal,