Index: lucene/core/src/java/org/apache/lucene/search/IndexSearcher.java
===================================================================
--- lucene/core/src/java/org/apache/lucene/search/IndexSearcher.java	(revision 1505274)
+++ lucene/core/src/java/org/apache/lucene/search/IndexSearcher.java	(working copy)
@@ -430,6 +430,10 @@
     if (limit == 0) {
       limit = 1;
     }
+    if (after != null && after.doc >= limit) {
+      throw new IllegalArgumentException("after.doc exceeds the number of documents in that reader: after.doc="
+          + after.doc + " limit=" + limit);
+    }
     nDocs = Math.min(nDocs, limit);
     
     if (executor == null) {
@@ -440,8 +444,7 @@
       final ExecutionHelper<TopDocs> runner = new ExecutionHelper<TopDocs>(executor);
     
       for (int i = 0; i < leafSlices.length; i++) { // search each sub
-        runner.submit(
-                      new SearcherCallableNoSort(lock, this, leafSlices[i], weight, after, nDocs, hq));
+        runner.submit(new SearcherCallableNoSort(lock, this, leafSlices[i], weight, after, nDocs, hq));
       }
 
       int totalHits = 0;
Index: lucene/core/src/test/org/apache/lucene/search/TestIndexSearcher.java
===================================================================
--- lucene/core/src/test/org/apache/lucene/search/TestIndexSearcher.java	(revision 1505274)
+++ lucene/core/src/test/org/apache/lucene/search/TestIndexSearcher.java	(working copy)
@@ -29,9 +29,11 @@
 import org.apache.lucene.index.Term;
 import org.apache.lucene.store.Directory;
 import org.apache.lucene.util.BytesRef;
+import org.apache.lucene.util.IOUtils;
 import org.apache.lucene.util.LuceneTestCase;
 import org.apache.lucene.util.NamedThreadFactory;
 import org.apache.lucene.util._TestUtil;
+import org.junit.Test;
 
 public class TestIndexSearcher extends LuceneTestCase {
   Directory dir;
@@ -116,4 +118,25 @@
     
     _TestUtil.shutdownExecutorService(service);
   }
+  
+  @Test
+  public void testSearchAfterPassedMaxDoc() throws Exception {
+    // LUCENE-5128: ensure we get a meaningful message if searchAfter exceeds maxDoc
+    Directory dir = newDirectory();
+    RandomIndexWriter w = new RandomIndexWriter(random(), dir);
+    w.addDocument(new Document());
+    IndexReader r = w.getReader();
+    w.close();
+    
+    IndexSearcher s = new IndexSearcher(r);
+    try {
+      s.searchAfter(new ScoreDoc(r.maxDoc(), 0.54f), new MatchAllDocsQuery(), 10);
+      fail("should have hit IllegalArgumentException when searchAfter exceeds maxDoc");
+    } catch (IllegalArgumentException e) {
+      // ok
+    } finally {
+      IOUtils.close(r, dir);
+    }
+  }
+  
 }