Can't use var element in Spring Web Flow definition?

I'm trying to declare a variable in my flow following the documentation, using

<var name="myVar" class="int" />

However, Eclipse highlights the var as an error, and I get a parser exception when running the flow (either from within Eclipse or from a standalone jar):

org.xml.sax.SAXParseException: cvc-complex-type.2.4.a: Invalid content was found starting with element 'var'. One of '{"http://ift.tt/1jwD1YA":input, "http://ift.tt/1jwD1YA":on-start, "http://ift.tt/1jwD1YA":action-state, "http://ift.tt/1jwD1YA":view-state, "http://ift.tt/1jwD1YA":decision-state, "http://ift.tt/1jwD1YA":subflow-state, "http://ift.tt/1jwD1YA":end-state, "http://ift.tt/1jwD1YA":global-transitions, "http://ift.tt/1jwD1YA":on-end, "http://ift.tt/1jwD1YA":output, "http://ift.tt/1jwD1YA":exception-handler, "http://ift.tt/1jwD1YA":bean-import}' is expected.
    at com.sun.org.apache.xerces.internal.util.ErrorHandlerWrapper.createSAXParseException(ErrorHandlerWrapper.java:203)
    at com.sun.org.apache.xerces.internal.util.ErrorHandlerWrapper.error(ErrorHandlerWrapper.java:134)
    at com.sun.org.apache.xerces.internal.impl.XMLErrorReporter.reportError(XMLErrorReporter.java:437)
    at com.sun.org.apache.xerces.internal.impl.XMLErrorReporter.reportError(XMLErrorReporter.java:368)
    at com.sun.org.apache.xerces.internal.impl.XMLErrorReporter.reportError(XMLErrorReporter.java:325)
    at com.sun.org.apache.xerces.internal.impl.xs.XMLSchemaValidator$XSIErrorReporter.reportError(XMLSchemaValidator.java:458)
    at com.sun.org.apache.xerces.internal.impl.xs.XMLSchemaValidator.reportSchemaError(XMLSchemaValidator.java:3237)
    at com.sun.org.apache.xerces.internal.impl.xs.XMLSchemaValidator.handleStartElement(XMLSchemaValidator.java:1796)
    at com.sun.org.apache.xerces.internal.impl.xs.XMLSchemaValidator.emptyElement(XMLSchemaValidator.java:766)
    at com.sun.org.apache.xerces.internal.impl.XMLNSDocumentScannerImpl.scanStartElement(XMLNSDocumentScannerImpl.java:356)
    at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl$FragmentContentDriver.next(XMLDocumentFragmentScannerImpl.java:2786)
    at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl.next(XMLDocumentScannerImpl.java:606)
    at com.sun.org.apache.xerces.internal.impl.XMLNSDocumentScannerImpl.next(XMLNSDocumentScannerImpl.java:117)
    at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanDocument(XMLDocumentFragmentScannerImpl.java:510)
    at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:848)
    at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:777)
    at com.sun.org.apache.xerces.internal.parsers.XMLParser.parse(XMLParser.java:141)
    at com.sun.org.apache.xerces.internal.parsers.DOMParser.parse(DOMParser.java:243)
    at com.sun.org.apache.xerces.internal.jaxp.DocumentBuilderImpl.parse(DocumentBuilderImpl.java:348)
    at javax.xml.parsers.DocumentBuilder.parse(DocumentBuilder.java:121)
    at org.springframework.webflow.engine.model.builder.xml.DefaultDocumentLoader.loadDocument(DefaultDocumentLoader.java:113)
    at org.springframework.webflow.engine.model.builder.xml.XmlFlowModelBuilder.init(XmlFlowModelBuilder.java:112)

I'm using the latest XSD:

<flow xmlns="http://ift.tt/1jwD1YA"
    xmlns:xsi="http://ift.tt/ra1lAU"
    xsi:schemaLocation="http://ift.tt/1jwD1YA
        http://ift.tt/1pZXDNv">

and I've verified that the 2.4 XSD both on the Spring server and in the jar do in fact contain the definition for the var element, right along with input, on-start, and the other working elements.

Any idea what may be the problem?