diff --git a/src/main/java/org/umlgraph/doclet/Options.java b/src/main/java/org/umlgraph/doclet/Options.java
index 8412964..2aa0f4b 100644
--- a/src/main/java/org/umlgraph/doclet/Options.java
+++ b/src/main/java/org/umlgraph/doclet/Options.java
@@ -98,7 +98,7 @@ public class Options implements Cloneable, OptionProvider {
     String nodeFontTagName = null;
     double nodeFontPackageSize = -1;
     String nodeFontPackageName = null;
-    Shape shape = new Shape();
+    Shape shape = Shape.CLASS;
     String bgColor = null;
     public String outputFileName = "graph.dot";
     String outputEncoding = "ISO-8859-1"; // TODO: default to UTF-8 now?
@@ -367,9 +367,9 @@ public class Options implements Cloneable, OptionProvider {
 	} else if (opt[0].equals("-!nodefillcolor")) {
 	    nodeFillColor = null;
 	} else if(opt[0].equals("-shape")) {
-	    shape = new Shape(opt[1]);
+	    shape = Shape.of(opt[1]);
 	} else if (opt[0].equals("-!shape")) {
-	    shape = new Shape();
+	    shape = Shape.CLASS;
 	} else if(opt[0].equals("-output")) {
 	    outputFileName = opt[1];
 	} else if (opt[0].equals("-!output")) {
diff --git a/src/main/java/org/umlgraph/doclet/Shape.java b/src/main/java/org/umlgraph/doclet/Shape.java
index e5db2eb..a3c0484 100644
--- a/src/main/java/org/umlgraph/doclet/Shape.java
+++ b/src/main/java/org/umlgraph/doclet/Shape.java
@@ -18,67 +18,71 @@
 
 package org.umlgraph.doclet;
 
+import java.util.HashMap;
+import java.util.Locale;
+
 /**
  * Properties of node shapes
  *
  * @version $Revision$
- * @author <a href="http://www.spinellis.gr">Diomidis Spinellis</a>
+ * @author Erich Schubert
  */
-public class Shape {
+public enum Shape {
+    CLASS(""), //
+    NOTE(", shape=note"), //
+    NODE(", shape=box3d"), //
+    COMPONENT(", shape=component"), //
+    PACKAGE(", shape=tab"), //
+    COLLABORATION(", shape=ellipse, style=dashed"), //
+    USECASE(", shape=ellipse"), //
+    ACTIVECLASS("");
 
-    /** Shape's UMLGraph name */
-    private String name;
+    /** Graphviz style */
+    public final String style;
 
-    /** Construct a default (class) Shape */
-    public Shape() {
-	name = "class";
-    }
+    /** Map for valid shape names */
+    private static final HashMap<String, Shape> index = new HashMap<String, Shape>(16);
 
-    /** Construct a Shape through the specified UMLGraph name */
-    public Shape(String n) {
-	name = n;
-	if (graphvizAttribute() == null) {
-	    System.err.println("Ignoring invalid shape " + n);
-	    name = "class";
+    /** Initialize the lookup index */
+    static {
+	for (Shape s : Shape.values()) {
+	    index.put(s.name(), s);
+	    index.put(s.name().toLowerCase(Locale.ROOT), s);
 	}
     }
 
     /**
-     * Return the GraphViz shape name corresponding to the shape
+     * Get the shape from a string. This allows both the uppercase and the lowercase
+     * name. Prefer this to {{@link #valueOf(String)} which only accepts uppercase.
+     *
+     * @param s String
+     * @return Shape
      */
-    public String graphvizAttribute() {
-	if (name.equals("class"))
-	    return "";		// Default; plaintext
-	else if (name.equals("note"))
-	    return ", shape=note";
-	else if (name.equals("node"))
-	    return ", shape=box3d";
-	else if (name.equals("component"))
-	    return ", shape=component";
-	else if (name.equals("package"))
-	    return ", shape=tab";
-	else if (name.equals("collaboration"))
-	    return ", shape=ellipse, style=dashed";
-	else if (name.equals("usecase"))
-	    return ", shape=ellipse";
-	else if (name.equals("activeclass"))
-	    return "";		// Default; plaintext
-	else
-	    return null;
+    public static Shape of(String s) {
+	Shape shp = index.get(s);
+	if (shp != null)
+	    return shp;
+	System.err.println("Ignoring invalid shape: " + s);
+	return CLASS;
+    }
+
+    /** Enum constructor, must be private! */
+    private Shape(String style) {
+	this.style = style;
     }
 
     /** Return the shape's GraphViz landing port */
-    String landingPort() {
-	return (name.equals("class") || name.equals("activeclass")) ? ":p" : "";
+    public String landingPort() {
+	return this == CLASS || this == ACTIVECLASS ? ":p" : "";
     }
 
     /** Return the table border required for the shape */
-    String extraColumn() {
-	return name.equals("activeclass") ? ("<td rowspan=\"10\"></td>") : "";
+    public String extraColumn() {
+	return this == Shape.ACTIVECLASS ? ("<td rowspan=\"10\"></td>") : "";
     }
 
     /** Return the cell border required for the shape */
-    String cellBorder() {
-	return (name.equals("class") || name.equals("activeclass")) ? "1" : "0";
+    public String cellBorder() {
+	return this == CLASS || this == ACTIVECLASS ? "1" : "0";
     }
 }
diff --git a/src/main/java/org/umlgraph/doclet/UmlGraph.java b/src/main/java/org/umlgraph/doclet/UmlGraph.java
index 221eebc..edd3825 100644
--- a/src/main/java/org/umlgraph/doclet/UmlGraph.java
+++ b/src/main/java/org/umlgraph/doclet/UmlGraph.java
@@ -84,7 +84,7 @@ public class UmlGraph {
 	commentOptions = new Options();
 	commentOptions.setOptions(root.options());
 	commentOptions.setOptions(findClass(root, "UMLNoteOptions"));
-	commentOptions.shape = new Shape("note");
+	commentOptions.shape = Shape.NOTE;
 
 	Options opt = new Options();
 	opt.setOptions(root.options());