diff --git a/nifi-nar-bundles/nifi-framework-bundle/nifi-framework/nifi-framework-core/src/main/java/org/apache/nifi/controller/repository/StandardProcessSession.java b/nifi-nar-bundles/nifi-framework-bundle/nifi-framework/nifi-framework-core/src/main/java/org/apache/nifi/controller/repository/StandardProcessSession.java
index 002bac932e..80c917cebe 100644
--- a/nifi-nar-bundles/nifi-framework-bundle/nifi-framework/nifi-framework-core/src/main/java/org/apache/nifi/controller/repository/StandardProcessSession.java
+++ b/nifi-nar-bundles/nifi-framework-bundle/nifi-framework/nifi-framework-core/src/main/java/org/apache/nifi/controller/repository/StandardProcessSession.java
@@ -2580,7 +2580,8 @@ public final class StandardProcessSession implements ProcessSession, ProvenanceE
                     cnfeThrown = true;
                     throw cnfe;
                 } finally {
-                    this.bytesWritten += countingOut.getBytesWritten();
+                    writtenToFlowFile = countingOut.getBytesWritten();
+                    this.bytesWritten += writtenToFlowFile;
                     this.bytesRead += countingIn.getBytesRead();
                     recursionSet.remove(source);
 
diff --git a/nifi-nar-bundles/nifi-framework-bundle/nifi-framework/nifi-framework-core/src/test/java/org/apache/nifi/controller/repository/TestStandardProcessSession.java b/nifi-nar-bundles/nifi-framework-bundle/nifi-framework/nifi-framework-core/src/test/java/org/apache/nifi/controller/repository/TestStandardProcessSession.java
index 8cc088d480..6f94994ef2 100644
--- a/nifi-nar-bundles/nifi-framework-bundle/nifi-framework/nifi-framework-core/src/test/java/org/apache/nifi/controller/repository/TestStandardProcessSession.java
+++ b/nifi-nar-bundles/nifi-framework-bundle/nifi-framework/nifi-framework-core/src/test/java/org/apache/nifi/controller/repository/TestStandardProcessSession.java
@@ -276,6 +276,65 @@ public class TestStandardProcessSession {
         assertEquals(0, numClaims);
     }
 
+    @Test
+    public void testModifyContentWithStreamCallbackHasCorrectSize() throws IOException {
+        final FlowFileRecord flowFileRecord = new StandardFlowFileRecord.Builder()
+            .id(1000L)
+            .addAttribute("uuid", "12345678-1234-1234-1234-123456789012")
+            .entryDate(System.currentTimeMillis())
+            .build();
+        flowFileQueue.put(flowFileRecord);
+        FlowFile original = session.get();
+        assertNotNull(original);
+
+        FlowFile child = session.write(original, (in, out) -> out.write("hello".getBytes()));
+        session.transfer(child);
+        session.commit();
+
+        final FlowFileRecord onQueue = flowFileQueue.poll(Collections.emptySet());
+        assertEquals(5, onQueue.getSize());
+    }
+
+    @Test
+    public void testModifyContentWithOutputStreamCallbackHasCorrectSize() throws IOException {
+        final FlowFileRecord flowFileRecord = new StandardFlowFileRecord.Builder()
+            .id(1000L)
+            .addAttribute("uuid", "12345678-1234-1234-1234-123456789012")
+            .entryDate(System.currentTimeMillis())
+            .build();
+        flowFileQueue.put(flowFileRecord);
+        FlowFile original = session.get();
+        assertNotNull(original);
+
+        FlowFile child = session.write(original, out -> out.write("hello".getBytes()));
+        session.transfer(child);
+        session.commit();
+
+        final FlowFileRecord onQueue = flowFileQueue.poll(Collections.emptySet());
+        assertEquals(5, onQueue.getSize());
+    }
+
+    @Test
+    public void testModifyContentWithAppendHasCorrectSize() throws IOException {
+        final FlowFileRecord flowFileRecord = new StandardFlowFileRecord.Builder()
+            .id(1000L)
+            .addAttribute("uuid", "12345678-1234-1234-1234-123456789012")
+            .entryDate(System.currentTimeMillis())
+            .build();
+        flowFileQueue.put(flowFileRecord);
+        FlowFile original = session.get();
+        assertNotNull(original);
+
+        FlowFile child = session.append(original, out -> out.write("hello".getBytes()));
+        session.transfer(child);
+        session.commit();
+
+        final FlowFileRecord onQueue = flowFileQueue.poll(Collections.emptySet());
+        assertEquals(5, onQueue.getSize());
+    }
+
+
+
     @Test
     public void testModifyContentThenRollback() throws IOException {
         assertEquals(0, contentRepo.getExistingClaims().size());