diff --git a/spec/ruby/optional/capi/string_spec.rb b/spec/ruby/optional/capi/string_spec.rb
index 818cb7b20cd5..834620b0aa43 100644
--- a/spec/ruby/optional/capi/string_spec.rb
+++ b/spec/ruby/optional/capi/string_spec.rb
@@ -1293,7 +1293,8 @@ def inspect
     end
 
     it "returns the same string as String#-@" do
-      @s.rb_enc_interned_str("hello", str.bytesize, Encoding::UTF_8).should.equal?(-"hello")
+      str = "hello"
+      @s.rb_enc_interned_str(str, str.bytesize, Encoding::UTF_8).should.equal?(-str)
     end
 
     ruby_bug "#20322", ""..."3.4" do