Index: main/resources/org/apache/maven/continuum/web/action/BuildDefinitionAction-saveBuildDefinition-validation.xml
===================================================================
--- main/resources/org/apache/maven/continuum/web/action/BuildDefinitionAction-saveBuildDefinition-validation.xml	(revision 0)
+++ main/resources/org/apache/maven/continuum/web/action/BuildDefinitionAction-saveBuildDefinition-validation.xml	(revision 0)
@@ -0,0 +1,30 @@
+<!--
+  ~ Licensed to the Apache Software Foundation (ASF) under one
+  ~ or more contributor license agreements.  See the NOTICE file
+  ~ distributed with this work for additional information
+  ~ regarding copyright ownership.  The ASF licenses this file
+  ~ to you under the Apache License, Version 2.0 (the
+  ~ "License"); you may not use this file except in compliance
+  ~ with the License.  You may obtain a copy of the License at
+  ~
+  ~   http://www.apache.org/licenses/LICENSE-2.0
+  ~
+  ~ Unless required by applicable law or agreed to in writing,
+  ~ software distributed under the License is distributed on an
+  ~ "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+  ~ KIND, either express or implied.  See the License for the
+  ~ specific language governing permissions and limitations
+  ~ under the License.
+  -->
+
+<!DOCTYPE validators PUBLIC
+    "-//OpenSymphony Group//XWork Validator 1.0.2//EN"
+    "http://www.opensymphony.com/xwork/xwork-validator-1.0.2.dtd">
+
+<validators>
+  <field name="buildFile">
+    <field-validator type="requiredstring">
+      <message key="buildDefinition.buildFile.required"/>
+    </field-validator>
+  </field>
+</validators>
Index: main/resources/org/apache/maven/continuum/web/action/BuildDefinitionAction.properties
===================================================================
--- main/resources/org/apache/maven/continuum/web/action/BuildDefinitionAction.properties	(revision 540409)
+++ main/resources/org/apache/maven/continuum/web/action/BuildDefinitionAction.properties	(working copy)
@@ -17,4 +17,4 @@
 # under the License.
 #
 
-buildDefinition.buildFile.required = Build file is required
+buildDefinition.buildFile.required = Build file is required and cannot contain spaces only
\ No newline at end of file