diff --git a/core/regexp.rbs b/core/regexp.rbs
index fd6d9b102..783d1e686 100644
--- a/core/regexp.rbs
+++ b/core/regexp.rbs
@@ -948,7 +948,7 @@ class Regexp
   #     "  x = y  " =~ /(?<lhs>\w+)\s*=\s*(?<rhs>\w+)/
   #     p lhs, rhs # undefined local variable
   #
-  def =~: (String? str) -> Integer?
+  def =~: (String? | Symbol | _ToStr str) -> Integer?
 
   # <!--
   #   rdoc-file=re.c
diff --git a/test/stdlib/Regexp_test.rb b/test/stdlib/Regexp_test.rb
index 7e5f7ea85..c67fc9dfb 100644
--- a/test/stdlib/Regexp_test.rb
+++ b/test/stdlib/Regexp_test.rb
@@ -87,6 +87,7 @@ def test_triple_equal
   def test_equal_tilde
     /at/ =~ "input data" #=> 7
     /ax/ =~ "input data" #=> nil
+    /a/ =~ :a            #=> 0
   end
 
   def test_casefold?