Index: lucene/facet/src/test/org/apache/lucene/facet/sortedset/TestSortedSetDocValuesFacets.java
===================================================================
--- lucene/facet/src/test/org/apache/lucene/facet/sortedset/TestSortedSetDocValuesFacets.java	(revision 1499437)
+++ lucene/facet/src/test/org/apache/lucene/facet/sortedset/TestSortedSetDocValuesFacets.java	(working copy)
@@ -33,6 +33,7 @@
 import org.apache.lucene.facet.search.FacetResult;
 import org.apache.lucene.facet.search.FacetsCollector;
 import org.apache.lucene.facet.taxonomy.CategoryPath;
+import org.apache.lucene.index.IndexReader;
 import org.apache.lucene.index.RandomIndexWriter;
 import org.apache.lucene.search.IndexSearcher;
 import org.apache.lucene.search.MatchAllDocsQuery;
@@ -145,4 +146,51 @@
     searcher.getIndexReader().close();
     dir.close();
   }
+
+  // LUCENE-5090
+  public void testStaleState() throws Exception {
+    assumeTrue("Test requires SortedSetDV support", defaultCodecSupportsSortedSet());
+    Directory dir = newDirectory();
+    RandomIndexWriter writer = new RandomIndexWriter(random(), dir);
+
+    SortedSetDocValuesFacetFields dvFields = new SortedSetDocValuesFacetFields();
+
+    Document doc = new Document();
+    dvFields.addFields(doc, Collections.singletonList(new CategoryPath("a", "foo")));
+    writer.addDocument(doc);
+
+    IndexReader r = writer.getReader();
+    SortedSetDocValuesReaderState state = new SortedSetDocValuesReaderState(r);
+
+    doc = new Document();
+    dvFields.addFields(doc, Collections.singletonList(new CategoryPath("a", "bar")));
+    writer.addDocument(doc);
+
+    doc = new Document();
+    dvFields.addFields(doc, Collections.singletonList(new CategoryPath("a", "baz")));
+    writer.addDocument(doc);
+
+    IndexSearcher searcher = newSearcher(writer.getReader());
+
+    List<FacetRequest> requests = new ArrayList<FacetRequest>();
+    requests.add(new CountFacetRequest(new CategoryPath("a"), 10));
+
+    FacetSearchParams fsp = new FacetSearchParams(requests);
+    
+    FacetsCollector c = FacetsCollector.create(new SortedSetDocValuesAccumulator(fsp, state));
+
+    searcher.search(new MatchAllDocsQuery(), c);
+
+    try {
+      c.getFacetResults();
+      fail("did not hit expected exception");
+    } catch (IllegalStateException ise) {
+      // expected
+    }
+
+    r.close();
+    writer.close();
+    searcher.getIndexReader().close();
+    dir.close();
+  }
 }
Index: lucene/facet/src/java/org/apache/lucene/facet/sortedset/SortedSetDocValuesAccumulator.java
===================================================================
--- lucene/facet/src/java/org/apache/lucene/facet/sortedset/SortedSetDocValuesAccumulator.java	(revision 1499437)
+++ lucene/facet/src/java/org/apache/lucene/facet/sortedset/SortedSetDocValuesAccumulator.java	(working copy)
@@ -35,9 +35,11 @@
 import org.apache.lucene.facet.search.FacetsAggregator;
 import org.apache.lucene.facet.search.FacetsCollector.MatchingDocs;
 import org.apache.lucene.facet.taxonomy.CategoryPath;
+import org.apache.lucene.index.AtomicReader;
 import org.apache.lucene.index.IndexReader;
 import org.apache.lucene.index.MultiDocValues.MultiSortedSetDocValues;
 import org.apache.lucene.index.MultiDocValues;
+import org.apache.lucene.index.ReaderUtil;
 import org.apache.lucene.index.SortedSetDocValues;
 import org.apache.lucene.util.BytesRef;
 import org.apache.lucene.util.PriorityQueue;
@@ -57,7 +59,7 @@
   final String field;
 
   public SortedSetDocValuesAccumulator(FacetSearchParams fsp, SortedSetDocValuesReaderState state) throws IOException {
-    super(fsp, null, null, new FacetArrays((int) state.getDocValues().getValueCount()));
+    super(fsp, null, null, new FacetArrays(state.getSize()));
     this.state = state;
     this.field = state.getField();
     dv = state.getDocValues();
@@ -90,13 +92,18 @@
       @Override
       public void aggregate(MatchingDocs matchingDocs, CategoryListParams clp, FacetArrays facetArrays) throws IOException {
 
-        SortedSetDocValues segValues = matchingDocs.context.reader().getSortedSetDocValues(field);
+        AtomicReader reader = matchingDocs.context.reader();
+        if (ReaderUtil.getTopLevelContext(matchingDocs.context().reader() != state.origReader) {
+          throw new IllegalStateException("the SortedSetDocValuesReaderState provided to this class does not match the reader being searched; you must create a new SortedSetDocValuesReaderState every time you open a new IndexReader");
+        }
+        
+        SortedSetDocValues segValues = reader.getSortedSetDocValues(field);
         if (segValues == null) {
           return;
         }
 
         final int[] counts = facetArrays.getIntArray();
-        final int maxDoc = matchingDocs.context.reader().maxDoc();
+        final int maxDoc = reader.maxDoc();
         assert maxDoc == matchingDocs.bits.length();
 
         if (dv instanceof MultiSortedSetDocValues) {
Index: lucene/facet/src/java/org/apache/lucene/facet/sortedset/SortedSetDocValuesReaderState.java
===================================================================
--- lucene/facet/src/java/org/apache/lucene/facet/sortedset/SortedSetDocValuesReaderState.java	(revision 1499437)
+++ lucene/facet/src/java/org/apache/lucene/facet/sortedset/SortedSetDocValuesReaderState.java	(working copy)
@@ -51,6 +51,7 @@
   private final String field;
   private final AtomicReader topReader;
   private final int valueCount;
+  final IndexReader origReader;
   final char separator;
   final String separatorRegex;
 
@@ -91,6 +92,7 @@
     this.field = fip.getCategoryListParams(null).field + FACET_FIELD_EXTENSION;
     this.separator = fip.getFacetDelimChar();
     this.separatorRegex = Pattern.quote(Character.toString(separator));
+    this.origReader = reader;
 
     // We need this to create thread-safe MultiSortedSetDV
     // per collector: