An IOException occurs because of an EOF when trying to get the term vectors from the hits. I am using multiple aliases. The problem appears to be due to the fact that org.compass.core.lucene.engine.DefaultLuceneSearchEngineHits is creating LuceneResources with a document number from a MultiSearcher (in getResource(int)). The problem with this is that when LuceneHelper goes to retrieve the term vector, the document number can be (and is) greater than the total number of documents so the index is accessed at an offset past the end of the file. For our purposes, we have temporarily modified DefaultLuceneSearchEngineHits.getResource(int) to get the sub-document number for the resource: ... int docId = hits.id; Searcher searcher = internalSearch.getSearcher(); if (searcher instanceof MultiSearcher) { docId = ((MultiSearcher) searcher).subDoc(docId); } ... I'm not sure what other ramifications this may have or how 'correct' the fix is but it appears to solve the issue for us. In attempting to create a test case in the Compass project's test framework, I discovered that this issue seems to be related to caching. I initially added a test case to org.compass.core.test.termfreqvector.simple1.TermFreqVectorMultiSubIndexTests but was unable to duplicate the issue. It turns out that I was unable to duplicate the issue because a NullFirstLevelCache was being used. To duplicate the issue as a Compass test I: 1. overrode AbstractTestCase.buildConf() because it programmatically sets the first-level cache to NullFirstLevelCache 2. modifed org.compass.core.test.compass.cfg.xml to set the first-level cache to DefaultFirstLevelCache instead of NullFirstLevelCache. Attached is my modified TermFreqVectorMultiSubIndexTests.java with the added test case testTermFreqVectorsMultiSubIndex() method, and the compass.cfg.xml that I used.