diff --git a/extensions/modeshape-search-lucene/src/main/java/org/modeshape/search/lucene/LuceneSearchEngine.java b/extensions/modeshape-search-lucene/src/main/java/org/modeshape/search/lucene/LuceneSearchEngine.java
index d26a942..798fdce 100644
--- a/extensions/modeshape-search-lucene/src/main/java/org/modeshape/search/lucene/LuceneSearchEngine.java
+++ b/extensions/modeshape-search-lucene/src/main/java/org/modeshape/search/lucene/LuceneSearchEngine.java
@@ -31,6 +31,9 @@ import java.util.Iterator;
 import java.util.LinkedList;
 import java.util.List;
 import java.util.Map;
+import java.util.concurrent.locks.Lock;
+import java.util.concurrent.locks.ReadWriteLock;
+import java.util.concurrent.locks.ReentrantReadWriteLock;
 import net.jcip.annotations.Immutable;
 import org.apache.lucene.analysis.Analyzer;
 import org.apache.lucene.analysis.standard.StandardAnalyzer;
@@ -113,6 +116,7 @@ public class LuceneSearchEngine extends AbstractLuceneSearchEngine<LuceneSearchW
     private final IndexRules rules;
     private final Analyzer analyzer;
     private final int maxDepthPerIndexRead;
+    private final ReadWriteLock processingLock = new ReentrantReadWriteLock();
 
     /**
      * Create a new instance of a {@link SearchEngine} that uses Lucene and a two-index design, and that stores the indexes using
@@ -222,7 +226,9 @@ public class LuceneSearchEngine extends AbstractLuceneSearchEngine<LuceneSearchW
                                                      Workspaces<LuceneSearchWorkspace> workspaces,
                                                      Observer observer,
                                                      boolean readOnly ) {
-        return new LuceneSearchProcessor(getSourceName(), context, workspaces, observer, null, readOnly);
+        final Lock lock = readOnly ? processingLock.readLock() : processingLock.writeLock();
+        lock.lock();
+        return new LuceneSearchProcessor(getSourceName(), context, workspaces, observer, null, readOnly, lock);
     }
 
     /**
diff --git a/extensions/modeshape-search-lucene/src/main/java/org/modeshape/search/lucene/LuceneSearchProcessor.java b/extensions/modeshape-search-lucene/src/main/java/org/modeshape/search/lucene/LuceneSearchProcessor.java
index f21a8f6..6043d84 100644
--- a/extensions/modeshape-search-lucene/src/main/java/org/modeshape/search/lucene/LuceneSearchProcessor.java
+++ b/extensions/modeshape-search-lucene/src/main/java/org/modeshape/search/lucene/LuceneSearchProcessor.java
@@ -23,6 +23,13 @@
  */
 package org.modeshape.search.lucene;
 
+import java.io.FileNotFoundException;
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Set;
+import java.util.concurrent.locks.Lock;
 import net.jcip.annotations.NotThreadSafe;
 import org.apache.lucene.queryParser.ParseException;
 import org.apache.lucene.search.Query;
@@ -55,13 +62,6 @@ import org.modeshape.graph.search.AbstractSearchEngine.Workspaces;
 import org.modeshape.graph.search.SearchEngineProcessor;
 import org.modeshape.search.lucene.AbstractLuceneSearchEngine.AbstractLuceneProcessor;
 
-import java.io.FileNotFoundException;
-import java.io.IOException;
-import java.util.ArrayList;
-import java.util.HashSet;
-import java.util.List;
-import java.util.Set;
-
 /**
  * Abstract {@link SearchEngineProcessor} implementation for the {@link LuceneSearchEngine}.
  */
@@ -71,13 +71,31 @@ public class LuceneSearchProcessor extends AbstractLuceneProcessor<LuceneSearchW
     protected static final Columns FULL_TEXT_RESULT_COLUMNS = new FullTextSearchResultColumns();
     private static final Logger logger = Logger.getLogger(LuceneSearchProcessor.class);
 
+    private final Lock lock;
+
     protected LuceneSearchProcessor( String sourceName,
                                      ExecutionContext context,
                                      Workspaces<LuceneSearchWorkspace> workspaces,
                                      Observer observer,
                                      DateTime now,
-                                     boolean readOnly ) {
+                                     boolean readOnly,
+                                     Lock lock ) {
         super(sourceName, context, workspaces, observer, now, readOnly);
+        this.lock = lock;
+    }
+
+    /**
+     * {@inheritDoc}
+     * 
+     * @see org.modeshape.graph.search.SearchEngineProcessor#close()
+     */
+    @Override
+    public void close() {
+        try {
+            super.close();
+        } finally {
+            this.lock.unlock();
+        }
     }
 
     /**
diff --git a/extensions/modeshape-search-lucene/src/test/java/org/modeshape/search/lucene/LuceneSearchSessionTest.java b/extensions/modeshape-search-lucene/src/test/java/org/modeshape/search/lucene/LuceneSearchSessionTest.java
index b1953bd..a94b6b7 100644
--- a/extensions/modeshape-search-lucene/src/test/java/org/modeshape/search/lucene/LuceneSearchSessionTest.java
+++ b/extensions/modeshape-search-lucene/src/test/java/org/modeshape/search/lucene/LuceneSearchSessionTest.java
@@ -26,6 +26,7 @@ package org.modeshape.search.lucene;
 import static org.hamcrest.core.Is.is;
 import static org.junit.Assert.assertThat;
 import static org.mockito.Mockito.mock;
+import java.util.concurrent.locks.ReentrantLock;
 import org.junit.Before;
 import org.junit.Test;
 import org.modeshape.graph.ExecutionContext;
@@ -47,7 +48,7 @@ public class LuceneSearchSessionTest {
         DateTime now = context.getValueFactories().getDateFactory().create();
         Workspaces<LuceneSearchWorkspace> workspaces = mock(Workspaces.class);
         LuceneSearchWorkspace workspace = mock(LuceneSearchWorkspace.class);
-        processor = new LuceneSearchProcessor("source", context, workspaces, observer, now, true);
+        processor = new LuceneSearchProcessor("source", context, workspaces, observer, now, true, new ReentrantLock());
         search = new LuceneSearchSession(workspace, processor);
     }