diff --git a/WHATSNEW b/WHATSNEW
index 63112a22e..f7898c968 100644
--- a/WHATSNEW
+++ b/WHATSNEW
@@ -557,6 +557,10 @@ If set to true, the process will be spawned. Bugzilla Report 5907.
 * <if/> and <unless/> attributes added to <param/> element of <style>
    Bugzilla Report 22044
 
+* <zip> and friends have a new attribute "keepcompression" that can be
+  used to incrementally build an archive mixing compressed and uncompressed
+  entries.
+
 Changes from Ant 1.5.2 to Ant 1.5.3
 ===================================
 
diff --git a/docs/manual/CoreTasks/ear.html b/docs/manual/CoreTasks/ear.html
index 5a6076f4e..58c7ae8c0 100644
--- a/docs/manual/CoreTasks/ear.html
+++ b/docs/manual/CoreTasks/ear.html
@@ -40,7 +40,19 @@ attributes of zipfilesets in a Zip or Jar task.)</p>
   </tr>
   <tr>
     <td valign="top">compress</td>
-    <td valign="top">Not only store data but also compress them, defaults to true</td>
+    <td valign="top">Not only store data but also compress them,
+    defaults to true.  Unless you set the <em>keepcompression</em>
+    attribute to false, this will apply to the entire archive, not
+    only the files you've added while updating.</td>
+    <td align="center" valign="top">No</td>
+  </tr>
+  <tr>
+    <td valign="top">keepcompression</td>
+    <td valign="top">For entries coming from existing archives (like
+    nested <em>zipfileset</em>s or while updating the archive), keep
+    the compression as it has been originally instead of using the
+    <em>compress</em> attribute.  Defaults false.  <em>Since Ant
+    1.6</em></td>
     <td align="center" valign="top">No</td>
   </tr>
   <tr>
diff --git a/docs/manual/CoreTasks/jar.html b/docs/manual/CoreTasks/jar.html
index ef2b31d67..61a1dc1d5 100644
--- a/docs/manual/CoreTasks/jar.html
+++ b/docs/manual/CoreTasks/jar.html
@@ -73,7 +73,19 @@ being wrapped and continued on the next line.
   </tr>
   <tr>
     <td valign="top">compress</td>
-    <td valign="top">Not only store data but also compress them, defaults to true</td>
+    <td valign="top">Not only store data but also compress them,
+    defaults to true.  Unless you set the <em>keepcompression</em>
+    attribute to false, this will apply to the entire archive, not
+    only the files you've added while updating.</td>
+    <td align="center" valign="top">No</td>
+  </tr>
+  <tr>
+    <td valign="top">keepcompression</td>
+    <td valign="top">For entries coming from existing archives (like
+    nested <em>zipfileset</em>s or while updating the archive), keep
+    the compression as it has been originally instead of using the
+    <em>compress</em> attribute.  Defaults false.  <em>Since Ant
+    1.6</em></td>
     <td align="center" valign="top">No</td>
   </tr>
   <tr>
diff --git a/docs/manual/CoreTasks/war.html b/docs/manual/CoreTasks/war.html
index 004d387c0..30c500e85 100644
--- a/docs/manual/CoreTasks/war.html
+++ b/docs/manual/CoreTasks/war.html
@@ -47,7 +47,19 @@ attributes of zipfilesets in a Zip or Jar task.)</p>
   </tr>
   <tr>
     <td valign="top">compress</td>
-    <td valign="top">Not only store data but also compress them, defaults to true</td>
+    <td valign="top">Not only store data but also compress them,
+    defaults to true.  Unless you set the <em>keepcompression</em>
+    attribute to false, this will apply to the entire archive, not
+    only the files you've added while updating.</td>
+    <td align="center" valign="top">No</td>
+  </tr>
+  <tr>
+    <td valign="top">keepcompression</td>
+    <td valign="top">For entries coming from existing archives (like
+    nested <em>zipfileset</em>s or while updating the archive), keep
+    the compression as it has been originally instead of using the
+    <em>compress</em> attribute.  Defaults false.  <em>Since Ant
+    1.6</em></td>
     <td align="center" valign="top">No</td>
   </tr>
   <tr>
diff --git a/docs/manual/CoreTasks/zip.html b/docs/manual/CoreTasks/zip.html
index b2808e2b0..3a4addc4d 100644
--- a/docs/manual/CoreTasks/zip.html
+++ b/docs/manual/CoreTasks/zip.html
@@ -89,7 +89,19 @@ versions of zip and unzip for many Unix and Unix-like systems.</p>
   </tr>
   <tr>
     <td valign="top">compress</td>
-    <td valign="top">Not only store data but also compress them, defaults to true</td>
+    <td valign="top">Not only store data but also compress them,
+    defaults to true.  Unless you set the <em>keepcompression</em>
+    attribute to false, this will apply to the entire archive, not
+    only the files you've added while updating.</td>
+    <td align="center" valign="top">No</td>
+  </tr>
+  <tr>
+    <td valign="top">keepcompression</td>
+    <td valign="top">For entries coming from existing archives (like
+    nested <em>zipfileset</em>s or while updating the archive), keep
+    the compression as it has been originally instead of using the
+    <em>compress</em> attribute.  Defaults false.  <em>Since Ant
+    1.6</em></td>
     <td align="center" valign="top">No</td>
   </tr>
   <tr>
diff --git a/src/main/org/apache/tools/ant/taskdefs/Zip.java b/src/main/org/apache/tools/ant/taskdefs/Zip.java
index abda0f44c..445cb5d05 100644
--- a/src/main/org/apache/tools/ant/taskdefs/Zip.java
+++ b/src/main/org/apache/tools/ant/taskdefs/Zip.java
@@ -140,6 +140,14 @@ public class Zip extends MatchingTask {
      */
     private String encoding;
 
+    /**
+     * Whether the original compression of entries coming from a ZIP
+     * archive should be kept (for example when updating an archive).
+     *
+     * @since Ant 1.6
+     */
+    private boolean keepCompression = false;
+
     /**
      * This is the name/location of where to
      * create the .zip file.
@@ -307,6 +315,16 @@ public class Zip extends MatchingTask {
         return encoding;
     }
 
+    /**
+     * Whether the original compression of entries coming from a ZIP
+     * archive should be kept (for example when updating an archive).
+     *
+     * @since Ant 1.6
+     */
+    public void setKeepCompression(boolean keep) {
+        keepCompression = keep;
+    }
+
     /**
      * validate and build
      */
@@ -631,11 +649,20 @@ public class Zip extends MatchingTask {
                     zipFile(f, zOut, prefix + name, fileMode);
                 } else if (!resources[i].isDirectory()) {
                     ZipEntry ze = zf.getEntry(resources[i].getName());
+                    
                     if (ze != null) {
-                        zipFile(zf.getInputStream(ze), zOut, prefix + name,
-                                ze.getTime(), zfs.getSrc(getProject()),
-                                zfs.hasFileModeBeenSet() ? fileMode
-                                                         : ze.getUnixMode());
+                        boolean oldCompress = doCompress;
+                        if (keepCompression) {
+                            doCompress = (ze.getMethod() == ZipEntry.DEFLATED);
+                        }
+                        try {
+                            zipFile(zf.getInputStream(ze), zOut, prefix + name,
+                                    ze.getTime(), zfs.getSrc(getProject()),
+                                    zfs.hasFileModeBeenSet() ? fileMode
+                                    : ze.getUnixMode());
+                        } finally {
+                            doCompress = oldCompress;
+                        }
                     }
                 }
             }
@@ -973,6 +1000,7 @@ public class Zip extends MatchingTask {
         if (!skipWriting) {
             ZipEntry ze = new ZipEntry(vPath);
             ze.setTime(lastModified);
+            ze.setMethod(doCompress ? ZipEntry.DEFLATED : ZipEntry.STORED);
 
             /*
             * ZipOutputStream.putNextEntry expects the ZipEntry to