diff --git a/builtin/builtin.mbti b/builtin/builtin.mbti
index e45ec029e..65dd2aabd 100644
--- a/builtin/builtin.mbti
+++ b/builtin/builtin.mbti
@@ -634,6 +634,7 @@ impl Double {
   to_int(Double) -> Int
   to_int64(Double) -> Int64
   to_json(Double) -> Json
+  to_uint64(Double) -> UInt64
   until(Double, Double, step~ : Double = .., inclusive~ : Bool = ..) -> Iter[Double]
   upto(Double, Double, inclusive~ : Bool = ..) -> Iter[Double] //deprecated
 }
diff --git a/double/double.mbti b/double/double.mbti
index 45a80e529..0a383e0b8 100644
--- a/double/double.mbti
+++ b/double/double.mbti
@@ -38,6 +38,7 @@ impl Double {
   to_be_bytes(Double) -> Bytes
   to_le_bytes(Double) -> Bytes
   to_string(Double) -> String
+  to_uint(Double) -> UInt
   trunc(Double) -> Double
 }
 impl Hash for Double