diff --git a/WHATSNEW b/WHATSNEW
index 92d8de49a..9eb64cfe6 100644
--- a/WHATSNEW
+++ b/WHATSNEW
@@ -19,6 +19,8 @@ Fixed bugs:
 * <javah>'s outputfile attribute will be resolved as relative to the
   projects basedir.
 
+* <antstructure> should create a valid DTD for propertyfile.operation.entry
+
 Changes from Ant 1.2 to Ant 1.3
 ===========================================
 
diff --git a/src/main/org/apache/tools/ant/taskdefs/AntStructure.java b/src/main/org/apache/tools/ant/taskdefs/AntStructure.java
index 4c632eb54..24add68b5 100644
--- a/src/main/org/apache/tools/ant/taskdefs/AntStructure.java
+++ b/src/main/org/apache/tools/ant/taskdefs/AntStructure.java
@@ -256,7 +256,9 @@ public class AntStructure extends Task {
                     EnumeratedAttribute ea = 
                         (EnumeratedAttribute)type.newInstance();
                     String[] values = ea.getValues();
-                    if (values == null || values.length == 0) {
+                    if (values == null
+                        || values.length == 0
+                        || !areNmtokens(values)) {
                         sb.append("CDATA ");
                     } else {
                         sb.append("(");
@@ -291,4 +293,35 @@ public class AntStructure extends Task {
     
     private void printTail(PrintWriter out) {}
 
+    /**
+     * Does this String match the XML-NMTOKEN production?
+     */
+    protected boolean isNmtoken(String s) {
+        for (int i = 0; i < s.length(); i++) {
+            char c = s.charAt(i);
+            // XXX - we are ommitting CombiningChar and Extender here
+            if (!Character.isLetterOrDigit(c) &&
+                c != '.' && c != '-' &&
+                c != '_' && c != ':') {
+                return false;
+            }
+        }
+        return true;
+    }
+
+    /**
+     * Do the Strings all match the XML-NMTOKEN production?
+     *
+     * <p>Otherwise they are not suitable as an enumerated attribute,
+     * for example.</p>
+     */
+    protected boolean areNmtokens(String[] s) {
+        for (int i = 0; i < s.length; i++) {
+            if (!isNmtoken(s[i])) {
+                return false;
+            }
+        }
+        return true;
+    }
+
 }