diff --git a/lucene/CHANGES.txt b/lucene/CHANGES.txt
index fc1fbbcf798..f4b8d287b1c 100644
--- a/lucene/CHANGES.txt
+++ b/lucene/CHANGES.txt
@@ -175,6 +175,9 @@ Improvements
   per hit in dependencies, ExpressionFunctionValues will no longer
   recompute already computed values (Haoyu Zhai)
 
+* LUCENE-9416: Fix CheckIndex to print an invalid non-zero norm as
+  unsigned long when detecting corruption.
+
 Optimizations
 ---------------------
 (No changes)
diff --git a/lucene/core/src/java/org/apache/lucene/index/CheckIndex.java b/lucene/core/src/java/org/apache/lucene/index/CheckIndex.java
index 79d68856f87..3b1f533bc47 100644
--- a/lucene/core/src/java/org/apache/lucene/index/CheckIndex.java
+++ b/lucene/core/src/java/org/apache/lucene/index/CheckIndex.java
@@ -1671,7 +1671,7 @@ public final class CheckIndex implements Closeable {
             }
             final long norm = norms.longValue();
             if (norm != 0 && visitedDocs.get(doc) == false) {
-              throw new RuntimeException("Document " + doc + " doesn't have terms according to postings but has a norm value that is not zero: " + norm);
+              throw new RuntimeException("Document " + doc + " doesn't have terms according to postings but has a norm value that is not zero: " + Long.toUnsignedString(norm));
             } else if (norm == 0 && visitedDocs.get(doc)) {
               throw new RuntimeException("Document " + doc + " has terms according to postings but its norm value is 0, which may only be used on documents that have no terms");
             }