1 files changed, 4 insertions, 3 deletions
diff --git a/spec/ruby/core/string/concat_spec.rb b/spec/ruby/core/string/concat_spec.rb
index 5f6daadad7..cbd7df54e2 100644
--- a/spec/ruby/core/string/concat_spec.rb
+++ b/spec/ruby/core/string/concat_spec.rb
@@ -5,21 +5,22 @@ require_relative 'shared/concat'
 describe "String#concat" do
   it_behaves_like :string_concat, :concat
   it_behaves_like :string_concat_encoding, :concat
+  it_behaves_like :string_concat_type_coercion, :concat
 
   it "takes multiple arguments" do
-    str = "hello "
+    str = +"hello "
     str.concat "wo", "", "rld"
     str.should == "hello world"
   end
 
   it "concatenates the initial value when given arguments contain 2 self" do
-    str = "hello"
+    str = +"hello"
     str.concat str, str
     str.should == "hellohellohello"
   end
 
   it "returns self when given no arguments" do
-    str = "hello"
+    str = +"hello"
     str.concat.should equal(str)
     str.should == "hello"
   end