diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 4da5ffa..6413fbb 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -25,7 +25,8 @@ jobs:
       - name: Install external renderers
         run: |
           sudo apt-get update
-          sudo apt-get install -y asciidoctor python3-docutils perl
+          sudo apt-get install -y asciidoctor python3-docutils perl ruby
+          rdoc --version
 
       - name: Build
         run: go build -v ./...
diff --git a/README.md b/README.md
index 8cfe6ac..f726e7c 100644
--- a/README.md
+++ b/README.md
@@ -37,7 +37,7 @@ The default registry comes with all supported formats pre-configured. Native for
 | Textile | .textile | consumer-provided (external) |
 | MediaWiki | .mediawiki, .wiki | consumer-provided (external) |
 | Creole | .creole | consumer-provided (external) |
-| RDoc | .rdoc | consumer-provided (external) |
+| RDoc | .rdoc | rdoc (external) |
 
 ## Format detection
 
@@ -85,6 +85,7 @@ The native formats (Markdown, Org-mode) need no external tools. For the others:
 | asciidoctor | `gem install asciidoctor` | AsciiDoc |
 | rst2html | `pip install docutils` or `apt install python3-docutils` | reStructuredText |
 | pod2html | Included with Perl | Pod |
+| rdoc | Included with Ruby | RDoc |
 
 ## Benchmarks
 
diff --git a/markup.go b/markup.go
index 9cd7532..b70f1b0 100644
--- a/markup.go
+++ b/markup.go
@@ -157,6 +157,7 @@ func NewDefaultRegistry() *Registry {
 
 	r.Register(FormatRDoc, NewExternalRenderer(ExternalConfig{
 		Command: "rdoc",
+		Args:    []string{"--pipe"},
 	}), ".rdoc")
 
 	return r
diff --git a/markup_test.go b/markup_test.go
index 011d008..ec9ad69 100644
--- a/markup_test.go
+++ b/markup_test.go
@@ -586,6 +586,7 @@ func TestRenderRDoc(t *testing.T) {
 		t.Skip("rdoc renderer not installed")
 	}
 	content := readTestdata(t, "README.rdoc")
+	t.Chdir(t.TempDir())
 	result, err := r.Render("README.rdoc", content)
 	if err != nil {
 		t.Fatalf("unexpected error: %v", err)
@@ -593,6 +594,18 @@ func TestRenderRDoc(t *testing.T) {
 	if result.Format != FormatRDoc {
 		t.Errorf("Format = %v, want FormatRDoc", result.Format)
 	}
+	for _, want := range []string{"<ul>", "<li>", "<p>One</p>", `<a href="http://github.com">absolute link</a>`, `<a href="rawr.html">relative link</a>`} {
+		if !strings.Contains(result.HTML, want) {
+			t.Errorf("expected %q in HTML, got: %s", want, result.HTML)
+		}
+	}
+	entries, err := os.ReadDir(".")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(entries) != 0 {
+		t.Errorf("renderer created files: %v", entries)
+	}
 }
 
 // --- Input size limit ---