diff --git a/lucene/CHANGES.txt b/lucene/CHANGES.txt
index 79b27e9d4051..39629386289c 100644
--- a/lucene/CHANGES.txt
+++ b/lucene/CHANGES.txt
@@ -165,6 +165,9 @@ Optimizations
 
 Bug Fixes
 ---------------------
+* Fix missing null check in RamUsageEstimator.sizeOf(Accountable) to be consistent
+  with sizeOf(String) and sizeOf(Accountable[]). (Tim Grein)
+
 * GITHUB#14049: Randomize KNN codec params in RandomCodec. Fixes scalar quantization div-by-zero
   when all values are identical. (Mike Sokolov)
 
diff --git a/lucene/core/src/java/org/apache/lucene/util/RamUsageEstimator.java b/lucene/core/src/java/org/apache/lucene/util/RamUsageEstimator.java
index 08b3cd1fb3e1..9041581efa49 100644
--- a/lucene/core/src/java/org/apache/lucene/util/RamUsageEstimator.java
+++ b/lucene/core/src/java/org/apache/lucene/util/RamUsageEstimator.java
@@ -425,9 +425,12 @@ private static long sizeOfObject(Object o, int depth, long defSize) {
 
   /**
    * Returns the size in bytes of the {@link Accountable} object, using its {@link
-   * Accountable#ramBytesUsed()} method.
+   * Accountable#ramBytesUsed()} method. Returns 0, if the {@link Accountable} object is null.
    */
   public static long sizeOf(Accountable accountable) {
+    if (accountable == null) {
+      return 0;
+    }
     return accountable.ramBytesUsed();
   }
 
diff --git a/lucene/core/src/test/org/apache/lucene/util/TestRamUsageEstimator.java b/lucene/core/src/test/org/apache/lucene/util/TestRamUsageEstimator.java
index 8e0bd13507ea..5ffb7e9c3e01 100644
--- a/lucene/core/src/test/org/apache/lucene/util/TestRamUsageEstimator.java
+++ b/lucene/core/src/test/org/apache/lucene/util/TestRamUsageEstimator.java
@@ -150,6 +150,11 @@ public void testMap() {
     assertEquals((double) actual, (double) estimated, (double) actual * errorFactor);
   }
 
+  public void testAccountable() {
+    assertEquals(0L, RamUsageEstimator.sizeOf((Accountable) null));
+    assertEquals(1L, RamUsageEstimator.sizeOf(new DummyAccountable()));
+  }
+
   public void testCollection() {
     List<Object> list = new ArrayList<>();
     list.add(1234L);
@@ -252,4 +257,11 @@ private static class HolderSubclass extends Holder {
   private static class HolderSubclass2 extends Holder {
     // empty, only inherits all fields -> size should be identical to superclass
   }
+
+  private static class DummyAccountable implements Accountable {
+    @Override
+    public long ramBytesUsed() {
+      return 1L;
+    }
+  }
 }