diff --git a/src/js/Node.js b/src/js/Node.js
index d3dfa41..e7c8a0a 100644
--- a/src/js/Node.js
+++ b/src/js/Node.js
@@ -379,7 +379,7 @@ Node.prototype.setField = function(field, fieldEditable) {
  */
 Node.prototype.getField = function() {
   if (this.field === undefined) {
-    this._getDomField();
+    this._getDomField(false);
   }
 
   return this.field;
@@ -1891,13 +1891,25 @@ Node.prototype._getDomField = function(silent) {
     this.fieldInnerText = util.getInnerText(this.dom.field);
   }
 
-  if (this.fieldInnerText != undefined) {
+  if (this.fieldInnerText !== undefined) {
     try {
       var field = this._unescapeHTML(this.fieldInnerText);
 
       if (field !== this.field) {
-        this.field = field;
-        this._debouncedOnChangeField();
+        var existingFieldNames = this.parent.getFieldNames(this);
+        var isDuplicate = existingFieldNames.indexOf(field) !== -1;
+
+        if (!isDuplicate) {
+          this.field = field;
+          this._debouncedOnChangeField();
+        }
+        else {
+          if (!silent) {
+            // fix duplicate field: change it into a unique name
+            this.field = util.findUniqueName(field, existingFieldNames);
+            this._debouncedOnChangeField();
+          }
+        }
       }
     }
     catch (err) {
@@ -1936,54 +1948,6 @@ Node.prototype._updateDomDefault = function () {
   }
 };
 
-/**
- * Validate this node and all it's childs
- * @return {Array.<{node: Node, error: {message: string}}>} Returns a list with duplicates
- */
-Node.prototype.validate = function () {
-  var errors = [];
-
-  // find duplicate keys
-  if (this.type === 'object') {
-    var keys = {};
-    var duplicateKeys = [];
-    for (var i = 0; i < this.childs.length; i++) {
-      var child = this.childs[i];
-      if (keys.hasOwnProperty(child.field)) {
-        duplicateKeys.push(child.field);
-      }
-      keys[child.field] = true;
-    }
-
-    if (duplicateKeys.length > 0) {
-      errors = this.childs
-          .filter(function (node) {
-            return duplicateKeys.indexOf(node.field) !== -1;
-          })
-          .map(function (node) {
-            return {
-              node: node,
-              error: {
-                message: translate('duplicateKey') + ' "' + node.field + '"'
-              }
-            }
-          });
-    }
-  }
-
-  // recurse over the childs
-  if (this.childs) {
-    for (var i = 0; i < this.childs.length; i++) {
-      var e = this.childs[i].validate();
-      if (e.length > 0) {
-        errors = errors.concat(e);
-      }
-    }
-  }
-
-  return errors;
-};
-
 /**
  * Clear the dom of the node
  */
@@ -2958,6 +2922,13 @@ Node.prototype.onEvent = function (event) {
   if (target == domField) {
     switch (type) {
       case 'blur':
+        this._getDomField(false);
+        this._updateDomField();
+        if (this.field) {
+          domField.innerHTML = this._escapeHTML(this.field);
+        }
+        break;
+
       case 'change':
         this._getDomField(true);
         this._updateDomField();
@@ -3462,6 +3433,25 @@ Node.prototype._showColorPicker = function () {
   }
 };
 
+/**
+ * Get all field names of an object
+ * @param {Node} [excludeNode] Optional node to be excluded from the returned field names
+ * @return {string[]}
+ */
+Node.prototype.getFieldNames = function (excludeNode) {
+  if (this.type === 'object') {
+    return this.childs
+        .filter(function (child) {
+          return child !== excludeNode;
+        })
+        .map(function (child) {
+          return child.field;
+        });
+  }
+
+  return [];
+}
+
 /**
  * Remove nodes
  * @param {Node[] | Node} nodes
@@ -3526,6 +3516,8 @@ Node.onDuplicate = function(nodes) {
     var afterNode = lastNode;
     var clones = nodes.map(function (node) {
       var clone = node.clone();
+      var existingFieldNames = node.parent.getFieldNames();
+      clone.field = util.findUniqueName(node.field, existingFieldNames);
       parent.insertAfter(clone, afterNode);
       afterNode = clone;
       return clone;
diff --git a/src/js/treemode.js b/src/js/treemode.js
index 2122682..10f73b4 100644
--- a/src/js/treemode.js
+++ b/src/js/treemode.js
@@ -577,9 +577,6 @@ treemode.validate = function () {
 
   var json = root.getValue();
 
-  // check for duplicate keys
-  var duplicateErrors = root.validate();
-
   // execute JSON schema validation
   var schemaErrors = [];
   if (this.validateSchema) {
@@ -611,7 +608,7 @@ treemode.validate = function () {
         .then(function (customValidationErrors) {
           // only apply when there was no other validation started whilst resolving async results
           if (seq === me.validationSequence) {
-            var errorNodes = [].concat(duplicateErrors, schemaErrors, customValidationErrors || []);
+            var errorNodes = [].concat(schemaErrors, customValidationErrors || []);
             me._renderValidationErrors(errorNodes);
           }
         })
diff --git a/src/js/util.js b/src/js/util.js
index bc14c3f..6bb4c94 100644
--- a/src/js/util.js
+++ b/src/js/util.js
@@ -1150,3 +1150,23 @@ exports.makeFieldTooltip = function (schema, locale) {
 
   return tooltip;
 }
+
+/**
+ * Find a unique name. Suffix the name with ' (copy)', '(copy 2)', etc
+ * until a unique name is found
+ * @param {string} name
+ * @param {Array} existingPropNames    Array with existing prop names
+ */
+exports.findUniqueName = function(name, existingPropNames) {
+  var strippedName = name.replace(/ \(copy( \d+)?\)$/, '')
+  var validName = strippedName
+  var i = 1
+
+  while (existingPropNames.indexOf(validName) !== -1) {
+    var copy = 'copy' + (i > 1 ? (' ' + i) : '')
+    validName = `${strippedName} (${copy})`
+    i++
+  }
+
+  return validName
+}
diff --git a/test/util.test.js b/test/util.test.js
index 4a32737..d46b6ef 100644
--- a/test/util.test.js
+++ b/test/util.test.js
@@ -224,5 +224,51 @@ describe('util', function () {
       assert.strictEqual(util.makeFieldTooltip({examples: ['foo']}, 'pt-BR'), 'Exemplos\n"foo"');
     });
   });
+
+  it('should find a unique name', function () {
+    assert.strictEqual(util.findUniqueName('other', [
+      'a',
+      'b',
+      'c'
+    ]), 'other')
+
+    assert.strictEqual(util.findUniqueName('b', [
+      'a',
+      'b',
+      'c'
+    ]), 'b (copy)')
+
+    assert.strictEqual(util.findUniqueName('b', [
+      'a',
+      'b',
+      'c',
+      'b (copy)'
+    ]), 'b (copy 2)')
+
+    assert.strictEqual(util.findUniqueName('b', [
+      'a',
+      'b',
+      'c',
+      'b (copy)',
+      'b (copy 2)'
+    ]), 'b (copy 3)')
+
+    assert.strictEqual(util.findUniqueName('b (copy)', [
+      'a',
+      'b',
+      'b (copy)',
+      'b (copy 2)',
+      'c'
+    ]), 'b (copy 3)')
+
+    assert.strictEqual(util.findUniqueName('b (copy 2)', [
+      'a',
+      'b',
+      'b (copy)',
+      'b (copy 2)',
+      'c'
+    ]), 'b (copy 3)')
+  })
+
   // TODO: thoroughly test all util methods
 });
\ No newline at end of file