diff --git a/flat/style/flat.editor.js b/flat/style/flat.editor.js
index 83c16a3..9917634 100644
--- a/flat/style/flat.editor.js
+++ b/flat/style/flat.editor.js
@@ -386,6 +386,16 @@ function addhigherorderfield(set, index, type) {
     } else if (folia_isspanrole(type)) {
         newchildannotation = {'type':type,'targets': []};
     }
+    if (folia_occurrences(type) == 1) {
+        //ensure we don't add a duplicate
+        var exists = false;
+        for (var i = 0; i < editdata[index].children.length; i++) {
+            if (editdata[index].children[i].type == type) {
+                alert("An annotation of this type already exists, there can be only one");
+                return false;
+            }
+        }
+    }
     if (newchildannotation !== null) {
         $('#higherorderfields' + index +  "placeholder")[0].outerHTML =
             "<tr class=\"higherorderrow\">" +
diff --git a/flat/style/folia.js b/flat/style/folia.js
index ddf02bf..c0bd430 100644
--- a/flat/style/folia.js
+++ b/flat/style/folia.js
@@ -194,11 +194,10 @@ function folia_required_spanroles(tag) {
     return spanroles;
 }
 
-}
 
 function folia_occurrences_class(elementclass) {
     /* Get the maximum amount of occurrences for this element class (0=unlimited) */
-    if ((foliaelements[elementclass]) && (foliaelements[elementclass].properties) && (foliaelements[elementclass].properties.occurrences)) {
+    if ((foliaelements[elementclass]) && (foliaelements[elementclass].properties) && (foliaelements[elementclass].properties.occurrences !== undefined)) {
         return foliaelements[elementclass].properties.occurrences;
     } else if (foliaelements[elementclass].ancestors.length >= 1) {
         return folia_occurrences_class(foliaelements[elementclass].ancestors[0]);