diff --git oak-segment-tar/src/main/java/org/apache/jackrabbit/oak/segment/file/FileStore.java oak-segment-tar/src/main/java/org/apache/jackrabbit/oak/segment/file/FileStore.java
index 7dd4667..90fc1f8 100644
--- oak-segment-tar/src/main/java/org/apache/jackrabbit/oak/segment/file/FileStore.java
+++ oak-segment-tar/src/main/java/org/apache/jackrabbit/oak/segment/file/FileStore.java
@@ -314,7 +314,7 @@ public class FileStore implements SegmentStore, Closeable {
             }
         }
 
-        long initialSize = size();
+        long initialSize = initialSize();
         this.approximateSize = new AtomicLong(initialSize);
         this.stats = new FileStoreStats(builder.getStatsProvider(), this, initialSize);
 
@@ -581,7 +581,7 @@ public class FileStore implements SegmentStore, Closeable {
         return dataFiles;
     }
 
-    public final long size() {
+    private long initialSize() {
         fileStoreLock.readLock().lock();
         try {
             long size = writeFile != null ? writeFile.length() : 0;
@@ -593,6 +593,10 @@ public class FileStore implements SegmentStore, Closeable {
             fileStoreLock.readLock().unlock();
         }
     }
+    
+    public final long size() {
+        return approximateSize.get();
+    }
 
     public int readerCount(){
         fileStoreLock.readLock().lock();
@@ -793,7 +797,6 @@ public class FileStore implements SegmentStore, Closeable {
         }
 
         long finalSize = size();
-        approximateSize.set(finalSize);
         stats.reclaimed(initialSize - finalSize);
         // FIXME OAK-4106: Reclaimed size reported by FileStore.cleanup is off
         gcListener.cleaned(initialSize - finalSize, finalSize);
@@ -1389,7 +1392,7 @@ public class FileStore implements SegmentStore, Closeable {
     }
 
     private void checkDiskSpace() {
-        long repositoryDiskSpace = approximateSize.get();
+        long repositoryDiskSpace = size();
         long availableDiskSpace = directory.getFreeSpace();
         boolean updated = gcOptions.isDiskSpaceSufficient(repositoryDiskSpace, availableDiskSpace);
         boolean previous = sufficientDiskSpace.getAndSet(updated);