diff --git a/lucene/CHANGES.txt b/lucene/CHANGES.txt
index ebe7bb12a8a..12c4dea136b 100644
--- a/lucene/CHANGES.txt
+++ b/lucene/CHANGES.txt
@@ -92,6 +92,9 @@ Bug fixes
   NullPointerException, if the synonym map is empty when creating
   SynonymFilter (帅广应 via Mike McCandless)
 
+* LUCENE-5432: EliasFanoDocIdSet: Fix number of index entry bits when the maximum
+  entry is a power of 2. (Paul Elschot via Adrien Grand)
+
 Test Framework
 
 * LUCENE-5449: Rename _TestUtil and _TestHelper to remove the leading _.
diff --git a/lucene/core/src/java/org/apache/lucene/util/packed/EliasFanoEncoder.java b/lucene/core/src/java/org/apache/lucene/util/packed/EliasFanoEncoder.java
index d55dd632af9..1079bf5be30 100644
--- a/lucene/core/src/java/org/apache/lucene/util/packed/EliasFanoEncoder.java
+++ b/lucene/core/src/java/org/apache/lucene/util/packed/EliasFanoEncoder.java
@@ -177,7 +177,7 @@ public class EliasFanoEncoder {
     this.numIndexEntries = (nIndexEntries >= 0) ? nIndexEntries : 0;
     long maxIndexEntry = maxHighValue + numValues - 1; // clear upper bits, set upper bits, start at zero
     this.nIndexEntryBits = (maxIndexEntry <= 0) ? 0
-                          : (64 - Long.numberOfLeadingZeros(maxIndexEntry - 1));
+                          : (64 - Long.numberOfLeadingZeros(maxIndexEntry));
     long numLongsForIndexBits = numLongsForBits(numIndexEntries * nIndexEntryBits);
     if (numLongsForIndexBits > Integer.MAX_VALUE) {
       throw new IllegalArgumentException("numLongsForIndexBits too large to index a long array: " + numLongsForIndexBits);