diff --git a/lib/slim/splat/builder.rb b/lib/slim/splat/builder.rb
index 84ecdc99..3d0b6afc 100644
--- a/lib/slim/splat/builder.rb
+++ b/lib/slim/splat/builder.rb
@@ -35,7 +35,7 @@ def attr(name, value)
         end
         if @attrs[name]
           if delim = @options[:merge_attrs][name]
-            @attrs[name] += delim + value.to_s
+            @attrs[name].concat(delim + value.to_s)
           else
             raise("Multiple #{name} attributes specified")
           end
diff --git a/test/rails/app/views/slim/splat_with_delimiter.slim b/test/rails/app/views/slim/splat_with_delimiter.slim
new file mode 100644
index 00000000..16775116
--- /dev/null
+++ b/test/rails/app/views/slim/splat_with_delimiter.slim
@@ -0,0 +1 @@
+.cute *{class: "nice"} Hello
\ No newline at end of file
diff --git a/test/rails/test/test_slim.rb b/test/rails/test/test_slim.rb
index 2fbfb548..dacf0311 100644
--- a/test/rails/test/test_slim.rb
+++ b/test/rails/test/test_slim.rb
@@ -94,4 +94,9 @@ class TestSlim < ActionDispatch::IntegrationTest
     get "/slim/splat"
     assert_html "<div id=\"splat\"><splat>Hello</splat></div>"
   end
+
+  test "splat with delimiter" do
+    get "/slim/splat_with_delimiter"
+    assert_html "<div class=\"cute nice\">Hello</div>"
+  end
 end