diff --git a/WHATSNEW b/WHATSNEW
index 342cf5669..fd76f14ab 100644
--- a/WHATSNEW
+++ b/WHATSNEW
@@ -34,6 +34,9 @@ Other changes:
  * Ant is now more lenient with ZIP extra fields and will be able to
    read archives that it failed to read in earlier versions.
 
+ * The <zip> family of tasks has been sped up for bigger archives.
+   Bugzilla Report 48755.
+
 Changes from Ant 1.8.0RC1 TO Ant 1.8.0
 ======================================
 
diff --git a/src/main/org/apache/tools/ant/taskdefs/Zip.java b/src/main/org/apache/tools/ant/taskdefs/Zip.java
index fe049c0e8..210378bea 100644
--- a/src/main/org/apache/tools/ant/taskdefs/Zip.java
+++ b/src/main/org/apache/tools/ant/taskdefs/Zip.java
@@ -1723,7 +1723,7 @@ public class Zip extends MatchingTask {
         throws IOException {
         // fromArchive is used in subclasses overriding this method
 
-        if (entries.contains(vPath)) {
+        if (entries.containsKey(vPath)) {
 
             if (duplicate.equals("preserve")) {
                 logWhenWriting(vPath + " already added, skipping",