diff --git a/lucene/core/src/java/org/apache/lucene/util/fst/BytesStore.java b/lucene/core/src/java/org/apache/lucene/util/fst/BytesStore.java
index 11810428d41..87b29fe8b7b 100644
--- a/lucene/core/src/java/org/apache/lucene/util/fst/BytesStore.java
+++ b/lucene/core/src/java/org/apache/lucene/util/fst/BytesStore.java
@@ -308,11 +308,6 @@ class BytesStore extends DataOutput implements FSTReader {
     return ((long) blocks.size() - 1) * blockSize + nextWrite;
   }
 
-  @Override
-  public long size() {
-    return getPosition();
-  }
-
   /** Set the position of this BytesStore, truncating or expanding if needed */
   public void setPosition(long newLen) {
     assert newLen >= 0;
diff --git a/lucene/core/src/java/org/apache/lucene/util/fst/FSTCompiler.java b/lucene/core/src/java/org/apache/lucene/util/fst/FSTCompiler.java
index 725b14614fa..9fbec138ce1 100644
--- a/lucene/core/src/java/org/apache/lucene/util/fst/FSTCompiler.java
+++ b/lucene/core/src/java/org/apache/lucene/util/fst/FSTCompiler.java
@@ -827,7 +827,7 @@ public class FSTCompiler<T> {
   }
 
   void finish(long newStartNode) {
-    assert newStartNode <= bytes.size();
+    assert newStartNode <= bytes.getPosition();
     if (fst.metadata.startNode != -1) {
       throw new IllegalStateException("already finished");
     }
diff --git a/lucene/core/src/java/org/apache/lucene/util/fst/FSTReader.java b/lucene/core/src/java/org/apache/lucene/util/fst/FSTReader.java
index f299fcb7558..b13b24b1a55 100644
--- a/lucene/core/src/java/org/apache/lucene/util/fst/FSTReader.java
+++ b/lucene/core/src/java/org/apache/lucene/util/fst/FSTReader.java
@@ -23,13 +23,6 @@ import org.apache.lucene.util.Accountable;
 /** Abstraction for reading bytes necessary for FST. */
 public interface FSTReader extends Accountable {
 
-  /**
-   * The raw size in bytes of the FST
-   *
-   * @return the FST size
-   */
-  long size();
-
   /**
    * Get the reverse BytesReader for this FST
    *
diff --git a/lucene/core/src/java/org/apache/lucene/util/fst/OffHeapFSTStore.java b/lucene/core/src/java/org/apache/lucene/util/fst/OffHeapFSTStore.java
index 6c102dff451..f88715b191c 100644
--- a/lucene/core/src/java/org/apache/lucene/util/fst/OffHeapFSTStore.java
+++ b/lucene/core/src/java/org/apache/lucene/util/fst/OffHeapFSTStore.java
@@ -56,7 +56,6 @@ public final class OffHeapFSTStore implements FSTStore {
     return BASE_RAM_BYTES_USED;
   }
 
-  @Override
   public long size() {
     return numBytes;
   }
diff --git a/lucene/core/src/java/org/apache/lucene/util/fst/OnHeapFSTStore.java b/lucene/core/src/java/org/apache/lucene/util/fst/OnHeapFSTStore.java
index b22c22ee4eb..2113c93f4c3 100644
--- a/lucene/core/src/java/org/apache/lucene/util/fst/OnHeapFSTStore.java
+++ b/lucene/core/src/java/org/apache/lucene/util/fst/OnHeapFSTStore.java
@@ -64,15 +64,6 @@ public final class OnHeapFSTStore implements FSTStore {
     return this;
   }
 
-  @Override
-  public long size() {
-    if (bytesArray != null) {
-      return bytesArray.length;
-    } else {
-      return bytes.getPosition();
-    }
-  }
-
   @Override
   public long ramBytesUsed() {
     long size = BASE_RAM_BYTES_USED;