diff --git a/WHATSNEW b/WHATSNEW
index 4bc3ca058..2e6116c2a 100644
--- a/WHATSNEW
+++ b/WHATSNEW
@@ -32,6 +32,9 @@ Fixed bugs:
 * UnknownElement.maybeConfigure always configured.
   Bugzilla report 40641.
 
+* no check for refid when prefix attribute is set in zipfileset.
+  Bugzilla report 30498.
+
 Other changes:
 --------------
 
diff --git a/src/main/org/apache/tools/ant/types/ArchiveFileSet.java b/src/main/org/apache/tools/ant/types/ArchiveFileSet.java
index 3eab55f5d..2c3b2a5bc 100755
--- a/src/main/org/apache/tools/ant/types/ArchiveFileSet.java
+++ b/src/main/org/apache/tools/ant/types/ArchiveFileSet.java
@@ -130,6 +130,7 @@ public abstract class ArchiveFileSet extends FileSet {
      * @param srcFile The archive from which to extract entries.
      */
     public void setSrc(File srcFile) {
+        checkAttributesAllowed();
         setSrcResource(new FileResource(srcFile));
     }
 
@@ -177,6 +178,7 @@ public abstract class ArchiveFileSet extends FileSet {
      * @param prefix The prefix to prepend to entries in the archive file.
      */
     public void setPrefix(String prefix) {
+        checkAttributesAllowed();
         if (!prefix.equals("") && !fullpath.equals("")) {
             throw new BuildException("Cannot set both fullpath and prefix attributes");
         }
@@ -202,6 +204,7 @@ public abstract class ArchiveFileSet extends FileSet {
      * @param fullpath the full pathname of the single entry in this fileset.
      */
     public void setFullpath(String fullpath) {
+        checkAttributesAllowed();
         if (!prefix.equals("") && !fullpath.equals("")) {
             throw new BuildException("Cannot set both fullpath and prefix attributes");
         }
@@ -304,6 +307,7 @@ public abstract class ArchiveFileSet extends FileSet {
      * @param octalString a <code>String</code> value
      */
     public void setFileMode(String octalString) {
+        checkAttributesAllowed();
         integerSetFileMode(Integer.parseInt(octalString, BASE_OCTAL));
     }
 
@@ -352,6 +356,7 @@ public abstract class ArchiveFileSet extends FileSet {
      * @param octalString a <code>String</code> value
      */
     public void setDirMode(String octalString) {
+        checkAttributesAllowed();
         integerSetDirMode(Integer.parseInt(octalString, BASE_OCTAL));
     }
 
diff --git a/src/main/org/apache/tools/ant/types/ZipFileSet.java b/src/main/org/apache/tools/ant/types/ZipFileSet.java
index f8df21593..a8e0e79fb 100644
--- a/src/main/org/apache/tools/ant/types/ZipFileSet.java
+++ b/src/main/org/apache/tools/ant/types/ZipFileSet.java
@@ -63,6 +63,7 @@ public class ZipFileSet extends ArchiveFileSet {
      * @since Ant 1.7
      */
     public void setEncoding(String enc) {
+        checkAttributesAllowed();
         this.encoding = enc;
     }
 
@@ -72,6 +73,14 @@ public class ZipFileSet extends ArchiveFileSet {
      * @since Ant 1.7
      */
     public String getEncoding() {
+        if (isReference()) {
+            AbstractFileSet ref = getRef(getProject());
+            if (ref instanceof ZipFileSet) {
+                return ((ZipFileSet) ref).getEncoding();
+            } else {
+                return null;
+            }
+        }
         return encoding;
     }