diff --git a/lucene/grouping/src/java/org/apache/lucene/search/grouping/TopGroups.java b/lucene/grouping/src/java/org/apache/lucene/search/grouping/TopGroups.java
index 20fcf266206b..4c238f786ba3 100644
--- a/lucene/grouping/src/java/org/apache/lucene/search/grouping/TopGroups.java
+++ b/lucene/grouping/src/java/org/apache/lucene/search/grouping/TopGroups.java
@@ -140,7 +140,7 @@ public static <T> TopGroups<T> merge(TopGroups<T>[] shardGroups, Sort groupSort,
     for(int groupIDX=0;groupIDX<numGroups;groupIDX++) {
       final T groupValue = shardGroups[0].groups[groupIDX].groupValue;
       //System.out.println("  merge groupValue=" + groupValue + " sortValues=" + Arrays.toString(shardGroups[0].groups[groupIDX].groupSortValues));
-      float maxScore = Float.MIN_VALUE;
+      float maxScore = Float.NaN;
       int totalHits = 0;
       double scoreSum = 0.0;
       for(int shardIDX=0;shardIDX<shardGroups.length;shardIDX++) {
@@ -169,9 +169,13 @@ public static <T> TopGroups<T> merge(TopGroups<T>[] shardGroups, Sort groupSort,
               shardGroupDocs.scoreDocs,
               docSort.getSort());
         }
-        if (! Float.isNaN(shardGroupDocs.maxScore)){
+        if (Float.isNaN(maxScore)){
+          maxScore = shardGroupDocs.maxScore;
+        }
+        else if (! Float.isNaN(shardGroupDocs.maxScore)){
           maxScore = Math.max(maxScore, shardGroupDocs.maxScore);
         }
+
         assert shardGroupDocs.totalHits.relation == Relation.EQUAL_TO;
         totalHits += shardGroupDocs.totalHits.value;
         scoreSum += shardGroupDocs.score;