diff --git a/pdfbox/src/main/java/org/apache/pdfbox/filter/CCITTFaxEncoderStream.java b/pdfbox/src/main/java/org/apache/pdfbox/filter/CCITTFaxEncoderStream.java
index 16e25b0e60b..4b8e30e0291 100644
--- a/pdfbox/src/main/java/org/apache/pdfbox/filter/CCITTFaxEncoderStream.java
+++ b/pdfbox/src/main/java/org/apache/pdfbox/filter/CCITTFaxEncoderStream.java
@@ -93,6 +93,10 @@ public void flush() throws IOException {
 
     @Override
     public void close() throws IOException {
+        // Release large data structures immediately so the GC can reclaim memory
+        // even if callers hold a reference to this COSDocument instance.
+        changesCurrentRow = null;
+        changesReferenceRow = null;
         stream.close();
     }