diff --git a/sig/big_decimal.rbs b/sig/big_decimal.rbs
index a0d0e80c..dd2a3c38 100644
--- a/sig/big_decimal.rbs
+++ b/sig/big_decimal.rbs
@@ -1237,7 +1237,9 @@ module Kernel
   # Raises an exception if `value` evaluates to a Float and `digits` is larger
   # than Float::DIG + 1.
   #
-  def self?.BigDecimal: (real | string | BigDecimal initial, ?int digits, ?exception: bool) -> BigDecimal
+  def self?.BigDecimal: (real | string | BigDecimal initial, ?int digits, ?exception: true) -> BigDecimal
+                      | (real | string | BigDecimal initial, ?int digits, exception: bool) -> BigDecimal?
+                      | (untyped initial, ?untyped digits, ?exception: bool) -> BigDecimal?
 end
 
 %a{annotate:rdoc:skip}