diff --git a/src/java.base/share/classes/java/util/zip/CRC32.java b/src/java.base/share/classes/java/util/zip/CRC32.java
index 944ccaa7e21..78050672ceb 100644
--- a/src/java.base/share/classes/java/util/zip/CRC32.java
+++ b/src/java.base/share/classes/java/util/zip/CRC32.java
@@ -31,6 +31,7 @@
 import sun.nio.ch.DirectBuffer;
 import jdk.internal.util.Preconditions;
 import jdk.internal.vm.annotation.IntrinsicCandidate;
+import org.jspecify.annotations.NullMarked;
 
 import static java.util.zip.ZipUtils.NIO_ACCESS;
 
@@ -43,6 +44,7 @@
  * @author      David Connelly
  * @since 1.1
  */
+@NullMarked
 public class CRC32 implements Checksum {
     private int crc;
 
diff --git a/src/java.base/share/classes/java/util/zip/GZIPOutputStream.java b/src/java.base/share/classes/java/util/zip/GZIPOutputStream.java
index cea0880fca6..d449717ff04 100644
--- a/src/java.base/share/classes/java/util/zip/GZIPOutputStream.java
+++ b/src/java.base/share/classes/java/util/zip/GZIPOutputStream.java
@@ -27,6 +27,7 @@
 
 import java.io.OutputStream;
 import java.io.IOException;
+import org.jspecify.annotations.NullMarked;
 
 /**
  * This class implements a stream filter for writing compressed data in
@@ -39,6 +40,7 @@
  * @since 1.1
  *
  */
+@NullMarked
 public class GZIPOutputStream extends DeflaterOutputStream {
     /**
      * CRC-32 of uncompressed data.