diff --git a/src/main/java/com/googlesource/gerrit/plugins/xdocs/XDocProjectConfig.java b/src/main/java/com/googlesource/gerrit/plugins/xdocs/XDocProjectConfig.java
index f3c931a..eb45cd7 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/xdocs/XDocProjectConfig.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/xdocs/XDocProjectConfig.java
@@ -22,6 +22,7 @@
 import com.google.inject.assistedinject.Assisted;
 
 import org.eclipse.jgit.lib.Config;
+import org.eclipse.jgit.lib.Constants;
 
 public class XDocProjectConfig {
   interface Factory {
@@ -29,6 +30,7 @@
   }
 
   private static final String SECTION_WEB = "web";
+  private static final String KEY_INDEX_REF = "indexRef";
   private static final String KEY_INDEX_FILE = "indexFile";
   private static final String DEFAULT_INDEX_FILE = "README.md";
 
@@ -40,6 +42,12 @@
     this.cfg = cfgFactory.getProjectPluginConfigWithInheritance(project, pluginName);
   }
 
+  String getIndexRef() {
+    return MoreObjects.firstNonNull(
+        cfg.getString(SECTION_WEB, null, KEY_INDEX_REF),
+        Constants.HEAD);
+  }
+
   String getIndexFile() {
     return MoreObjects.firstNonNull(
         cfg.getString(SECTION_WEB, null, KEY_INDEX_FILE),
diff --git a/src/main/java/com/googlesource/gerrit/plugins/xdocs/XDocServlet.java b/src/main/java/com/googlesource/gerrit/plugins/xdocs/XDocServlet.java
index eea1cf6..f557bee 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/xdocs/XDocServlet.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/xdocs/XDocServlet.java
@@ -141,7 +141,10 @@
     try {
       ProjectControl projectControl = projectControlFactory.validateFor(key.project);
       String rev = key.revision;
-      if (rev == null || Constants.HEAD.equals(rev)) {
+      if (rev == null) {
+        rev = cfg.getIndexRef();
+      }
+      if (Constants.HEAD.equals(rev)) {
         rev = getHead.get().apply(new ProjectResource(projectControl));
       } else  {
         if (!ObjectId.isId(rev)) {
diff --git a/src/main/resources/Documentation/config.md b/src/main/resources/Documentation/config.md
index aef00c5..0a3f97e 100644
--- a/src/main/resources/Documentation/config.md
+++ b/src/main/resources/Documentation/config.md
@@ -11,9 +11,25 @@
 
 ```
   [web]
+    indexRef = master
     indexFile = Documentation/README.md
 ```
 
+<a id="webIndexRef">
+web.indexRef
+:	The reference from which the documentation should be loaded if a
+	revision is not specified.
+
+	The documentation links in the project list will link to the index
+	file in this reference.
+
+	For branches the `refs/heads/` prefix may be omitted, all other
+	refs must be fully specified.
+
+	Inherited from the parent project if not specified.
+
+	Default: `HEAD`
+
 <a id="webIndexFile">
 web.indexFile
 :	The documentation file that serves as entry point for the project