Does Websphere Commerce 7 support JSTL 1.1 XML in widgets?

I have made a new blank widget and added it to a page. All the JSTL tags work normally in its JSP, but trying to do for example

<%@ taglib uri="http://ift.tt/O45vfj" prefix="x" %>
<x:set var="test"/>

results in an UnresolvableException

[19/11/14 17:16:45:617 FET] 0000001f LoggingHelper E /GenericJSPPageError.jsp - $requestScope:EC_device
                             org.apache.taglibs.standard.tag.common.xml.UnresolvableException: $requestScope:EC_device
at org.apache.taglibs.standard.tag.common.xml.XPathUtil$JstlVariableContext.notNull(XPathUtil.java:377)
at org.apache.taglibs.standard.tag.common.xml.XPathUtil$JstlVariableContext.getVariableValue(XPathUtil.java:322)
at org.apache.taglibs.standard.tag.common.xml.XPathUtil$JstlVariableContext.getVariableOrParam(XPathUtil.java:241)
at org.apache.taglibs.standard.tag.common.xml.XPathUtil.fillVarStack(XPathUtil.java:792)
at org.apache.taglibs.standard.tag.common.xml.XPathUtil.selectNodes(XPathUtil.java:536)
at org.apache.taglibs.standard.tag.common.xml.SetTag.doStartTag(SetTag.java:69)
...

I also have no idea what EC_device is and where it is coming from. JSTL XML tags are not used anywhere else in the project, so I cannot verify whether they work at all, and hence that is what I'm asking.