diff --git a/gcloud-java-contrib/gcloud-java-nio/src/main/java/com/google/cloud/storage/contrib/nio/CloudStorageFileSystem.java b/gcloud-java-contrib/gcloud-java-nio/src/main/java/com/google/cloud/storage/contrib/nio/CloudStorageFileSystem.java
index 80004792d2f8..13fdb18864b8 100644
--- a/gcloud-java-contrib/gcloud-java-nio/src/main/java/com/google/cloud/storage/contrib/nio/CloudStorageFileSystem.java
+++ b/gcloud-java-contrib/gcloud-java-nio/src/main/java/com/google/cloud/storage/contrib/nio/CloudStorageFileSystem.java
@@ -145,10 +145,12 @@ public CloudStoragePath getPath(String first, String... more) {
    * Does nothing.
    */
   @Override
-  public void close() {}
+  public void close() throws IOException {
+    // TODO(#809): Synchronously close all channels associated with this FileSystem instance.
+  }
 
   /**
-   * Returns {@code true}.
+   * Returns {@code true}, even if you previously called the {@link #close()} method.
    */
   @Override
   public boolean isOpen() {
diff --git a/gcloud-java-contrib/gcloud-java-nio/src/test/java/com/google/cloud/storage/contrib/nio/CloudStorageFileSystemProviderTest.java b/gcloud-java-contrib/gcloud-java-nio/src/test/java/com/google/cloud/storage/contrib/nio/CloudStorageFileSystemProviderTest.java
index e2ade4a1adb1..79e3bc82dfa3 100644
--- a/gcloud-java-contrib/gcloud-java-nio/src/test/java/com/google/cloud/storage/contrib/nio/CloudStorageFileSystemProviderTest.java
+++ b/gcloud-java-contrib/gcloud-java-nio/src/test/java/com/google/cloud/storage/contrib/nio/CloudStorageFileSystemProviderTest.java
@@ -391,7 +391,7 @@ public void testExists_trailingSlash() {
   }
 
   @Test
-  public void testExists_trailingSlash_disablePseudoDirectories() {
+  public void testExists_trailingSlash_disablePseudoDirectories() throws IOException  {
     try (CloudStorageFileSystem fs = forBucket("military", usePseudoDirectories(false))) {
       assertThat(Files.exists(fs.getPath("fashion/"))).isFalse();
     }
@@ -547,7 +547,7 @@ public void testIsDirectory_trailingSlash_alwaysTrue() {
   }
 
   @Test
-  public void testIsDirectory_trailingSlash_pseudoDirectoriesDisabled_false() {
+  public void testIsDirectory_trailingSlash_pseudoDirectoriesDisabled_false() throws IOException  {
     try (CloudStorageFileSystem fs = forBucket("doodle", usePseudoDirectories(false))) {
       assertThat(Files.isDirectory(fs.getPath("fundir/"))).isFalse();
     }
diff --git a/gcloud-java-contrib/gcloud-java-nio/src/test/java/com/google/cloud/storage/contrib/nio/CloudStoragePathTest.java b/gcloud-java-contrib/gcloud-java-nio/src/test/java/com/google/cloud/storage/contrib/nio/CloudStoragePathTest.java
index 4a1c40c9b28d..173a8047340a 100644
--- a/gcloud-java-contrib/gcloud-java-nio/src/test/java/com/google/cloud/storage/contrib/nio/CloudStoragePathTest.java
+++ b/gcloud-java-contrib/gcloud-java-nio/src/test/java/com/google/cloud/storage/contrib/nio/CloudStoragePathTest.java
@@ -52,7 +52,7 @@ public void before() {
   }
 
   @Test
-  public void testCreate_neverRemoveExtraSlashes() {
+  public void testCreate_neverRemoveExtraSlashes() throws IOException {
     try (CloudStorageFileSystem fs = CloudStorageFileSystem.forBucket("doodle")) {
       assertThat(fs.getPath("lol//cat").toString()).isEqualTo("lol//cat");
       assertThat((Object) fs.getPath("lol//cat")).isEqualTo(fs.getPath("lol//cat"));
@@ -60,7 +60,7 @@ public void testCreate_neverRemoveExtraSlashes() {
   }
 
   @Test
-  public void testCreate_preservesTrailingSlash() {
+  public void testCreate_preservesTrailingSlash() throws IOException {
     try (CloudStorageFileSystem fs = CloudStorageFileSystem.forBucket("doodle")) {
       assertThat(fs.getPath("lol/cat/").toString()).isEqualTo("lol/cat/");
       assertThat((Object) fs.getPath("lol/cat/")).isEqualTo(fs.getPath("lol/cat/"));
@@ -68,7 +68,7 @@ public void testCreate_preservesTrailingSlash() {
   }
 
   @Test
-  public void testGetGcsFilename_empty_notAllowed() {
+  public void testGetGcsFilename_empty_notAllowed() throws IOException {
     try (CloudStorageFileSystem fs = CloudStorageFileSystem.forBucket("doodle")) {
       thrown.expect(IllegalArgumentException.class);
       fs.getPath("").getBlobId();
@@ -76,21 +76,21 @@ public void testGetGcsFilename_empty_notAllowed() {
   }
 
   @Test
-  public void testGetGcsFilename_stripsPrefixSlash() {
+  public void testGetGcsFilename_stripsPrefixSlash() throws IOException {
     try (CloudStorageFileSystem fs = CloudStorageFileSystem.forBucket("doodle")) {
       assertThat(fs.getPath("/hi").getBlobId().name()).isEqualTo("hi");
     }
   }
 
   @Test
-  public void testGetGcsFilename_overrideStripPrefixSlash_doesntStripPrefixSlash() {
+  public void testGetGcsFilename_overrideStripPrefixSlash_doesntStripPrefixSlash() throws IOException {
     try (CloudStorageFileSystem fs = CloudStorageFileSystem.forBucket("doodle", stripPrefixSlash(false))) {
       assertThat(fs.getPath("/hi").getBlobId().name()).isEqualTo("/hi");
     }
   }
 
   @Test
-  public void testGetGcsFilename_extraSlashes_throwsIae() {
+  public void testGetGcsFilename_extraSlashes_throwsIae() throws IOException {
     try (CloudStorageFileSystem fs = CloudStorageFileSystem.forBucket("doodle")) {
       thrown.expect(IllegalArgumentException.class);
       fs.getPath("a//b").getBlobId().name();
@@ -98,14 +98,14 @@ public void testGetGcsFilename_extraSlashes_throwsIae() {
   }
 
   @Test
-  public void testGetGcsFilename_overridepermitEmptyPathComponents() {
+  public void testGetGcsFilename_overridepermitEmptyPathComponents() throws IOException {
     try (CloudStorageFileSystem fs = CloudStorageFileSystem.forBucket("doodle", permitEmptyPathComponents(true))) {
       assertThat(fs.getPath("a//b").getBlobId().name()).isEqualTo("a//b");
     }
   }
 
   @Test
-  public void testGetGcsFilename_freaksOutOnExtraSlashesAndDotDirs() {
+  public void testGetGcsFilename_freaksOutOnExtraSlashesAndDotDirs() throws IOException {
     try (CloudStorageFileSystem fs = CloudStorageFileSystem.forBucket("doodle")) {
       thrown.expect(IllegalArgumentException.class);
       fs.getPath("a//b/..").getBlobId().name();
@@ -113,7 +113,7 @@ public void testGetGcsFilename_freaksOutOnExtraSlashesAndDotDirs() {
   }
 
   @Test
-  public void testNameCount() {
+  public void testNameCount() throws IOException {
     try (CloudStorageFileSystem fs = CloudStorageFileSystem.forBucket("doodle")) {
       assertThat(fs.getPath("").getNameCount()).isEqualTo(1);
       assertThat(fs.getPath("/").getNameCount()).isEqualTo(0);
@@ -124,7 +124,7 @@ public void testNameCount() {
   }
 
   @Test
-  public void testGetName() {
+  public void testGetName() throws IOException {
     try (CloudStorageFileSystem fs = CloudStorageFileSystem.forBucket("doodle")) {
       assertThat(fs.getPath("").getName(0).toString()).isEqualTo("");
       assertThat(fs.getPath("/hi").getName(0).toString()).isEqualTo("hi");
@@ -133,7 +133,7 @@ public void testGetName() {
   }
 
   @Test
-  public void testGetName_negative_throwsIae() {
+  public void testGetName_negative_throwsIae() throws IOException {
     try (CloudStorageFileSystem fs = CloudStorageFileSystem.forBucket("doodle")) {
       thrown.expect(IllegalArgumentException.class);
       fs.getPath("angel").getName(-1);
@@ -141,7 +141,7 @@ public void testGetName_negative_throwsIae() {
   }
 
   @Test
-  public void testGetName_overflow_throwsIae() {
+  public void testGetName_overflow_throwsIae() throws IOException {
     try (CloudStorageFileSystem fs = CloudStorageFileSystem.forBucket("doodle")) {
       thrown.expect(IllegalArgumentException.class);
       fs.getPath("angel").getName(1);
@@ -149,7 +149,7 @@ public void testGetName_overflow_throwsIae() {
   }
 
   @Test
-  public void testIterator() {
+  public void testIterator() throws IOException {
     try (CloudStorageFileSystem fs = CloudStorageFileSystem.forBucket("doodle")) {
       assertThat(Iterables.get(fs.getPath("/dog/mog"), 0).toString()).isEqualTo("dog");
       assertThat(Iterables.get(fs.getPath("/dog/mog"), 1).toString()).isEqualTo("mog");
@@ -160,7 +160,7 @@ public void testIterator() {
   }
 
   @Test
-  public void testNormalize() {
+  public void testNormalize() throws IOException {
     try (CloudStorageFileSystem fs = CloudStorageFileSystem.forBucket("doodle")) {
       assertThat(fs.getPath("/").normalize().toString()).isEqualTo("/");
       assertThat(fs.getPath("a/x/../b/x/..").normalize().toString()).isEqualTo("a/b/");
@@ -170,7 +170,7 @@ public void testNormalize() {
   }
 
   @Test
-  public void testNormalize_dot_becomesBlank() {
+  public void testNormalize_dot_becomesBlank() throws IOException {
     try (CloudStorageFileSystem fs = CloudStorageFileSystem.forBucket("doodle")) {
       assertThat(fs.getPath("").normalize().toString()).isEqualTo("");
       assertThat(fs.getPath(".").normalize().toString()).isEqualTo("");
@@ -178,14 +178,14 @@ public void testNormalize_dot_becomesBlank() {
   }
 
   @Test
-  public void testNormalize_trailingSlash_isPreserved() {
+  public void testNormalize_trailingSlash_isPreserved() throws IOException {
     try (CloudStorageFileSystem fs = CloudStorageFileSystem.forBucket("doodle")) {
       assertThat(fs.getPath("o/").normalize().toString()).isEqualTo("o/");
     }
   }
 
   @Test
-  public void testNormalize_doubleDot_becomesBlank() {
+  public void testNormalize_doubleDot_becomesBlank() throws IOException {
     try (CloudStorageFileSystem fs = CloudStorageFileSystem.forBucket("doodle")) {
       assertThat(fs.getPath("..").normalize().toString()).isEqualTo("");
       assertThat(fs.getPath("../..").normalize().toString()).isEqualTo("");
@@ -193,14 +193,14 @@ public void testNormalize_doubleDot_becomesBlank() {
   }
 
   @Test
-  public void testNormalize_extraSlashes_getRemoved() {
+  public void testNormalize_extraSlashes_getRemoved() throws IOException {
     try (CloudStorageFileSystem fs = CloudStorageFileSystem.forBucket("doodle")) {
       assertThat(fs.getPath("//life///b/good//").normalize().toString()).isEqualTo("/life/b/good/");
     }
   }
 
   @Test
-  public void testToRealPath_hasDotDir_throwsIae() {
+  public void testToRealPath_hasDotDir_throwsIae() throws IOException {
     try (CloudStorageFileSystem fs = CloudStorageFileSystem.forBucket("doodle")) {
       fs.getPath("a/hi./b").toRealPath();
       fs.getPath("a/.hi/b").toRealPath();
@@ -211,7 +211,7 @@ public void testToRealPath_hasDotDir_throwsIae() {
   }
 
   @Test
-  public void testToRealPath_hasDotDotDir_throwsIae() {
+  public void testToRealPath_hasDotDotDir_throwsIae() throws IOException {
     try (CloudStorageFileSystem fs = CloudStorageFileSystem.forBucket("doodle")) {
       fs.getPath("a/hi../b").toRealPath();
       fs.getPath("a/..hi/b").toRealPath();
@@ -222,7 +222,7 @@ public void testToRealPath_hasDotDotDir_throwsIae() {
   }
 
   @Test
-  public void testToRealPath_extraSlashes_throwsIae() {
+  public void testToRealPath_extraSlashes_throwsIae() throws IOException {
     try (CloudStorageFileSystem fs = CloudStorageFileSystem.forBucket("doodle")) {
       thrown.expect(IllegalArgumentException.class);
       thrown.expectMessage("extra slashes");
@@ -231,7 +231,7 @@ public void testToRealPath_extraSlashes_throwsIae() {
   }
 
   @Test
-  public void testToRealPath_overridePermitEmptyPathComponents_extraSlashes_slashesRemain() {
+  public void testToRealPath_overridePermitEmptyPathComponents_extraSlashes_slashesRemain() throws IOException {
     try (CloudStorageFileSystem fs = CloudStorageFileSystem.forBucket("doodle", permitEmptyPathComponents(true))) {
       assertThat(fs.getPath("/life///b/./good/").toRealPath().toString())
           .isEqualTo("life///b/./good/");
@@ -239,7 +239,7 @@ public void testToRealPath_overridePermitEmptyPathComponents_extraSlashes_slashe
   }
 
   @Test
-  public void testToRealPath_permitEmptyPathComponents_doesNotNormalize() {
+  public void testToRealPath_permitEmptyPathComponents_doesNotNormalize() throws IOException {
     try (CloudStorageFileSystem fs = CloudStorageFileSystem.forBucket("doodle", permitEmptyPathComponents(true))) {
       assertThat(fs.getPath("a").toRealPath().toString()).isEqualTo("a");
       assertThat(fs.getPath("a//b").toRealPath().toString()).isEqualTo("a//b");
@@ -248,14 +248,14 @@ public void testToRealPath_permitEmptyPathComponents_doesNotNormalize() {
   }
 
   @Test
-  public void testToRealPath_withWorkingDirectory_makesAbsolute() {
+  public void testToRealPath_withWorkingDirectory_makesAbsolute() throws IOException {
     try (CloudStorageFileSystem fs = CloudStorageFileSystem.forBucket("doodle", workingDirectory("/lol"))) {
       assertThat(fs.getPath("a").toRealPath().toString()).isEqualTo("lol/a");
     }
   }
 
   @Test
-  public void testToRealPath_disableStripPrefixSlash_makesPathAbsolute() {
+  public void testToRealPath_disableStripPrefixSlash_makesPathAbsolute() throws IOException {
     try (CloudStorageFileSystem fs = CloudStorageFileSystem.forBucket("doodle", stripPrefixSlash(false))) {
       assertThat(fs.getPath("a").toRealPath().toString()).isEqualTo("/a");
       assertThat(fs.getPath("/a").toRealPath().toString()).isEqualTo("/a");
@@ -263,21 +263,21 @@ public void testToRealPath_disableStripPrefixSlash_makesPathAbsolute() {
   }
 
   @Test
-  public void testToRealPath_trailingSlash_getsPreserved() {
+  public void testToRealPath_trailingSlash_getsPreserved() throws IOException {
     try (CloudStorageFileSystem fs = CloudStorageFileSystem.forBucket("doodle")) {
       assertThat(fs.getPath("a/b/").toRealPath().toString()).isEqualTo("a/b/");
     }
   }
 
   @Test
-  public void testNormalize_empty_returnsEmpty() {
+  public void testNormalize_empty_returnsEmpty() throws IOException {
     try (CloudStorageFileSystem fs = CloudStorageFileSystem.forBucket("doodle")) {
       assertThat(fs.getPath("").normalize().toString()).isEqualTo("");
     }
   }
 
   @Test
-  public void testNormalize_preserveTrailingSlash() {
+  public void testNormalize_preserveTrailingSlash() throws IOException {
     try (CloudStorageFileSystem fs = CloudStorageFileSystem.forBucket("doodle")) {
       assertThat(fs.getPath("a/b/../c/").normalize().toString()).isEqualTo("a/c/");
       assertThat(fs.getPath("a/b/./c/").normalize().toString()).isEqualTo("a/b/c/");
@@ -285,7 +285,7 @@ public void testNormalize_preserveTrailingSlash() {
   }
 
   @Test
-  public void testGetParent_preserveTrailingSlash() {
+  public void testGetParent_preserveTrailingSlash() throws IOException {
     try (CloudStorageFileSystem fs = CloudStorageFileSystem.forBucket("doodle")) {
       assertThat(fs.getPath("a/b/c").getParent().toString()).isEqualTo("a/b/");
       assertThat(fs.getPath("a/b/c/").getParent().toString()).isEqualTo("a/b/");
@@ -297,7 +297,7 @@ public void testGetParent_preserveTrailingSlash() {
   }
 
   @Test
-  public void testGetRoot() {
+  public void testGetRoot() throws IOException {
     try (CloudStorageFileSystem fs = CloudStorageFileSystem.forBucket("doodle")) {
       assertThat(fs.getPath("/hello").getRoot().toString()).isEqualTo("/");
       assertThat((Object) fs.getPath("hello").getRoot()).isNull();
@@ -305,7 +305,7 @@ public void testGetRoot() {
   }
 
   @Test
-  public void testRelativize() {
+  public void testRelativize() throws IOException {
     try (CloudStorageFileSystem fs = CloudStorageFileSystem.forBucket("doodle")) {
       assertThat(
               fs.getPath("/foo/bar/lol/cat").relativize(fs.getPath("/foo/a/b/../../c")).toString())
@@ -314,7 +314,7 @@ public void testRelativize() {
   }
 
   @Test
-  public void testRelativize_providerMismatch() {
+  public void testRelativize_providerMismatch() throws IOException {
     try (CloudStorageFileSystem gcs = CloudStorageFileSystem.forBucket("doodle")) {
       thrown.expect(ProviderMismatchException.class);
       gcs.getPath("/etc").relativize(FileSystems.getDefault().getPath("/dog"));
@@ -323,7 +323,7 @@ public void testRelativize_providerMismatch() {
 
   @Test
   @SuppressWarnings("ReturnValueIgnored") // testing that an Exception is thrown
-  public void testRelativize_providerMismatch2() {
+  public void testRelativize_providerMismatch2() throws IOException {
     try (CloudStorageFileSystem gcs = CloudStorageFileSystem.forBucket("doodle")) {
       thrown.expect(ProviderMismatchException.class);
       gcs.getPath("/dog").relativize(FileSystems.getDefault().getPath("/etc"));
@@ -331,7 +331,7 @@ public void testRelativize_providerMismatch2() {
   }
 
   @Test
-  public void testResolve() {
+  public void testResolve() throws IOException {
     try (CloudStorageFileSystem fs = CloudStorageFileSystem.forBucket("doodle")) {
       assertThat(fs.getPath("/hi").resolve("there").toString()).isEqualTo("/hi/there");
       assertThat(fs.getPath("hi").resolve("there").toString()).isEqualTo("hi/there");
@@ -339,7 +339,7 @@ public void testResolve() {
   }
 
   @Test
-  public void testResolve_providerMismatch() {
+  public void testResolve_providerMismatch() throws IOException {
     try (CloudStorageFileSystem gcs = CloudStorageFileSystem.forBucket("doodle")) {
       thrown.expect(ProviderMismatchException.class);
       gcs.getPath("etc").resolve(FileSystems.getDefault().getPath("/dog"));
@@ -347,7 +347,7 @@ public void testResolve_providerMismatch() {
   }
 
   @Test
-  public void testIsAbsolute() {
+  public void testIsAbsolute() throws IOException {
     try (CloudStorageFileSystem fs = CloudStorageFileSystem.forBucket("doodle")) {
       assertThat(fs.getPath("/hi").isAbsolute()).isTrue();
       assertThat(fs.getPath("hi").isAbsolute()).isFalse();
@@ -355,7 +355,7 @@ public void testIsAbsolute() {
   }
 
   @Test
-  public void testToAbsolutePath() {
+  public void testToAbsolutePath() throws IOException {
     try (CloudStorageFileSystem fs = CloudStorageFileSystem.forBucket("doodle")) {
       assertThat((Object) fs.getPath("/hi").toAbsolutePath()).isEqualTo(fs.getPath("/hi"));
       assertThat((Object) fs.getPath("hi").toAbsolutePath()).isEqualTo(fs.getPath("/hi"));
@@ -363,14 +363,14 @@ public void testToAbsolutePath() {
   }
 
   @Test
-  public void testToAbsolutePath_withWorkingDirectory() {
+  public void testToAbsolutePath_withWorkingDirectory() throws IOException {
     try (CloudStorageFileSystem fs = CloudStorageFileSystem.forBucket("doodle", workingDirectory("/lol"))) {
       assertThat(fs.getPath("a").toAbsolutePath().toString()).isEqualTo("/lol/a");
     }
   }
 
   @Test
-  public void testGetFileName() {
+  public void testGetFileName() throws IOException {
     try (CloudStorageFileSystem fs = CloudStorageFileSystem.forBucket("doodle")) {
       assertThat(fs.getPath("/hi/there").getFileName().toString()).isEqualTo("there");
       assertThat(fs.getPath("military/fashion/show").getFileName().toString()).isEqualTo("show");
@@ -378,7 +378,7 @@ public void testGetFileName() {
   }
 
   @Test
-  public void testCompareTo() {
+  public void testCompareTo() throws IOException {
     try (CloudStorageFileSystem fs = CloudStorageFileSystem.forBucket("doodle")) {
       assertThat(fs.getPath("/hi/there").compareTo(fs.getPath("/hi/there"))).isEqualTo(0);
       assertThat(fs.getPath("/hi/there").compareTo(fs.getPath("/hi/therf"))).isEqualTo(-1);
@@ -387,7 +387,7 @@ public void testCompareTo() {
   }
 
   @Test
-  public void testStartsWith() {
+  public void testStartsWith() throws IOException {
     try (CloudStorageFileSystem fs = CloudStorageFileSystem.forBucket("doodle")) {
       assertThat(fs.getPath("/hi/there").startsWith(fs.getPath("/hi/there"))).isTrue();
       assertThat(fs.getPath("/hi/there").startsWith(fs.getPath("/hi/therf"))).isFalse();
@@ -400,7 +400,7 @@ public void testStartsWith() {
   }
 
   @Test
-  public void testEndsWith() {
+  public void testEndsWith() throws IOException {
     try (CloudStorageFileSystem fs = CloudStorageFileSystem.forBucket("doodle")) {
       assertThat(fs.getPath("/hi/there").endsWith(fs.getPath("there"))).isTrue();
       assertThat(fs.getPath("/hi/there").endsWith(fs.getPath("therf"))).isFalse();
@@ -441,7 +441,7 @@ public void testRelativize_willWorkWithRecursiveCopy() throws IOException {
   }
 
   @Test
-  public void testToFile_unsupported() {
+  public void testToFile_unsupported() throws IOException {
     try (CloudStorageFileSystem fs = CloudStorageFileSystem.forBucket("doodle")) {
       Path path = fs.getPath("/lol");
       thrown.expect(UnsupportedOperationException.class);
@@ -450,7 +450,7 @@ public void testToFile_unsupported() {
   }
 
   @Test
-  public void testEquals() {
+  public void testEquals() throws IOException {
     try (CloudStorageFileSystem fs = CloudStorageFileSystem.forBucket("doodle")) {
       new EqualsTester()
           // These are obviously equal.
@@ -466,7 +466,7 @@ public void testEquals() {
   }
 
   @Test
-  public void testEquals_currentDirectoryIsTakenIntoConsideration() {
+  public void testEquals_currentDirectoryIsTakenIntoConsideration() throws IOException {
     try (CloudStorageFileSystem fs = CloudStorageFileSystem.forBucket("doodle", workingDirectory("/hello"))) {
       new EqualsTester()
           .addEqualityGroup(fs.getPath("cat"), fs.getPath("/hello/cat"))
@@ -476,7 +476,7 @@ public void testEquals_currentDirectoryIsTakenIntoConsideration() {
   }
 
   @Test
-  public void testNullness() throws NoSuchMethodException, SecurityException {
+  public void testNullness() throws IOException, NoSuchMethodException, SecurityException {
     try (CloudStorageFileSystem fs = CloudStorageFileSystem.forBucket("doodle")) {
       NullPointerTester tester = new NullPointerTester();
       tester.ignore(CloudStoragePath.class.getMethod("equals", Object.class));