diff --git a/.travis.yml b/.travis.yml
index 7b43b6822..e526c902f 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -2,8 +2,19 @@ language: java
 notifications:
   email: false
 before_install: chmod +x gradlew
-install: ./gradlew setupCIWorkspace -S
-matrix:
-  include:
-  - jdk: oraclejdk7
-    script: ./gradlew build -S
\ No newline at end of file
+install: ./gradlew setupCIWorkspace -s
+script: ./gradlew build -s
+jdk:
+  - oraclejdk8
+  - oraclejdk7
+  - openjdk6
+# Caching for Gradle files, prevents hitting Maven too much.
+before_cache:
+  - rm -f $HOME/.gradle/caches/modules-2/modules-2.lock
+cache:
+  directories:
+    - $HOME/.gradle/caches/
+    - $HOME/.gradle/wrapper/
+
+# Faster builds without sudo.
+sudo: false
diff --git a/worldedit-core/src/main/java/com/sk89q/worldedit/util/io/Closer.java b/worldedit-core/src/main/java/com/sk89q/worldedit/util/io/Closer.java
index 2e733c6ab..6b5c37efe 100644
--- a/worldedit-core/src/main/java/com/sk89q/worldedit/util/io/Closer.java
+++ b/worldedit-core/src/main/java/com/sk89q/worldedit/util/io/Closer.java
@@ -29,6 +29,7 @@ import java.util.ArrayDeque;
 import java.util.Deque;
 import java.util.logging.Level;
 import java.util.logging.Logger;
+import java.util.zip.ZipFile;
 
 import static com.google.common.base.Preconditions.checkNotNull;
 
@@ -55,6 +56,7 @@ public final class Closer implements Closeable {
 
     // only need space for 2 elements in most cases, so try to use the smallest array possible
     private final Deque<Closeable> stack = new ArrayDeque<Closeable>(4);
+    private final Deque<ZipFile> zipStack = new ArrayDeque<ZipFile>(4);
     private Throwable thrown;
 
     @VisibleForTesting Closer(Suppressor suppressor) {
@@ -73,6 +75,17 @@ public final class Closer implements Closeable {
         return closeable;
     }
 
+    /**
+     * Registers the given {@code zipFile} to be closed when this {@code Closer} is
+     * {@linkplain #close closed}.
+     *
+     * @return the given {@code closeable}
+     */
+    public <Z extends ZipFile> Z register(Z zipFile) {
+        zipStack.push(zipFile);
+        return zipFile;
+    }
+
     /**
      * Stores the given throwable and rethrows it. It will be rethrown as is if it is an
      * {@code IOException}, {@code RuntimeException} or {@code Error}. Otherwise, it will be rethrown
@@ -161,6 +174,18 @@ public final class Closer implements Closeable {
                 }
             }
         }
+        while (!zipStack.isEmpty()) {
+            ZipFile zipFile = zipStack.pop();
+            try {
+                zipFile.close();
+            } catch (Throwable e) {
+                if (throwable == null) {
+                    throwable = e;
+                } else {
+                    suppressor.suppress(zipFile, throwable, e);
+                }
+            }
+        }
 
         if (thrown == null && throwable != null) {
             Throwables.propagateIfPossible(throwable, IOException.class);
@@ -177,7 +202,7 @@ public final class Closer implements Closeable {
          * the given closeable. {@code thrown} is the exception that is actually being thrown from the
          * method. Implementations of this method should not throw under any circumstances.
          */
-        void suppress(Closeable closeable, Throwable thrown, Throwable suppressed);
+        void suppress(Object closeable, Throwable thrown, Throwable suppressed);
     }
 
     /**
@@ -188,7 +213,7 @@ public final class Closer implements Closeable {
         static final LoggingSuppressor INSTANCE = new LoggingSuppressor();
 
         @Override
-        public void suppress(Closeable closeable, Throwable thrown, Throwable suppressed) {
+        public void suppress(Object closeable, Throwable thrown, Throwable suppressed) {
             // log to the same place as Closeables
             logger.log(Level.WARNING, "Suppressing exception thrown when closing " + closeable, suppressed);
         }
@@ -217,7 +242,7 @@ public final class Closer implements Closeable {
         }
 
         @Override
-        public void suppress(Closeable closeable, Throwable thrown, Throwable suppressed) {
+        public void suppress(Object closeable, Throwable thrown, Throwable suppressed) {
             // ensure no exceptions from addSuppressed
             if (thrown == suppressed) {
                 return;