diff --git a/strconv/double.mbt b/strconv/double.mbt
index 726e16e5e..f79bb210a 100644
--- a/strconv/double.mbt
+++ b/strconv/double.mbt
@@ -36,7 +36,7 @@ let max_exponent_fast_path : Int64 = 22L
 /// TODO: For `f32` it is 17, but we don't have `f32` yet.
 let max_exponent_disguised_fast_path : Int64 = 37L
 
-let max_mantissa_fast_path : UInt64 = lsl(2UL, mantissa_explicit_bits)
+let max_mantissa_fast_path : UInt64 = 2UL.lsl(mantissa_explicit_bits)
 
 pub fn parse_double(str : String) -> Double!String {
   if str.length() == 0 {
diff --git a/strconv/number.mbt b/strconv/number.mbt
index 587059d39..13dff2578 100644
--- a/strconv/number.mbt
+++ b/strconv/number.mbt
@@ -209,10 +209,6 @@ fn parse_inf_nan(s : String) -> (Double, Int)? {
   None
 }
 
-fn lsl(a : UInt64, b : Int) -> UInt64 {
-  a.to_int64().lsl(b).to_uint64()
-}
-
 /// Returns None if the multiplication might overflow (there are some false-negative corner cases).
 /// Otherwise, returns Some(m), where m = self * b.
 fn checked_mul(a : UInt64, b : UInt64) -> UInt64? {