[Open] java.lang.ClassCastException: org.apache.http.message

We get the following exception when trying to run the maven-soapui-pro plugin with proxy settings configured in the settings file. We are using version 4.5.1 of the plugin:
18:18:56,116 ERROR [SoapUI] An error occured [org.apache.http.message.BasicHttpRequest cannot be cast to org.apache.http.impl.client.RequestWrapper], see error log for details
java.lang.ClassCastException: org.apache.http.message.BasicHttpRequest cannot be cast to org.apache.http.impl.client.RequestWrapper
at com.eviware.soapui.impl.wsdl.support.http.HeadderRequestInterceptor.process(HeadderRequestInterceptor.java:42)
at org.apache.http.protocol.ImmutableHttpProcessor.process(ImmutableHttpProcessor.java:108)
at org.apache.http.protocol.HttpRequestExecutor.preProcess(HttpRequestExecutor.java:174)
at com.eviware.soapui.impl.wsdl.support.http.HttpClientSupport$SoapUIHttpRequestExecutor.preProcess(HttpClientSupport.java:106)
at org.apache.http.impl.client.DefaultRequestDirector.createTunnelToTarget(DefaultRequestDirector.java:830)
at org.apache.http.impl.client.DefaultRequestDirector.establishRoute(DefaultRequestDirector.java:739)
at org.apache.http.impl.client.DefaultRequestDirector.tryConnect(DefaultRequestDirector.java:565)
at org.apache.http.impl.client.DefaultRequestDirector.execute(DefaultRequestDirector.java:415)
at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:820)
at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:754)
at com.eviware.soapui.impl.wsdl.support.http.HttpClientSupport$Helper.execute(HttpClientSupport.java:236)
at com.eviware.soapui.impl.wsdl.support.http.HttpClientSupport.execute(HttpClientSupport.java:345)
at com.eviware.soapui.impl.wsdl.submit.transports.http.HttpClientRequestTransport.sendRequest(HttpClientRequestTransport.java:241)
at com.eviware.soapui.impl.wsdl.WsdlSubmit.run(WsdlSubmit.java:123)
at com.eviware.soapui.impl.wsdl.WsdlSubmit.submitRequest(WsdlSubmit.java:76)
at com.eviware.soapui.impl.rest.RestRequest.submit(RestRequest.java:209)
at com.eviware.soapui.impl.wsdl.teststeps.RestTestRequestStep.run(RestTestRequestStep.java:898)
at com.eviware.soapui.impl.wsdl.support.AbstractTestCaseRunner.runTestStep(AbstractTestCaseRunner.java:238)
at com.eviware.soapui.impl.wsdl.testcase.WsdlTestCaseRunner.runCurrentTestStep(WsdlTestCaseRunner.java:48)
at com.eviware.soapui.impl.wsdl.support.AbstractTestCaseRunner.internalRun(AbstractTestCaseRunner.java:147)
at com.eviware.soapui.impl.wsdl.support.AbstractTestCaseRunner.internalRun(AbstractTestCaseRunner.java:42)
at com.eviware.soapui.impl.wsdl.support.AbstractTestRunner.run(AbstractTestRunner.java:135)
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:441)
at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:303)
at java.util.concurrent.FutureTask.run(FutureTask.java:138)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
at java.lang.Thread.run(Thread.java:619)

From googling around it seems like this issue might be fixed in the nightly-build, but I don't know how I would integrate the nightly build to run with maven plugin. Any advice?

Thanks,
Scott