diff --git a/tools/android_library_cacher.py b/tools/android_library_cacher.py
index 564448a050042acb205a98ae0c4b280aa7b61b30..a0813979eee57cada9608b8e09200496b2bd6d58 100755
--- a/tools/android_library_cacher.py
+++ b/tools/android_library_cacher.py
@@ -57,6 +57,8 @@ def main():
         dest_dir = os.path.dirname(dest_file)
         if not os.path.exists(dest_dir):
             os.makedirs(dest_dir)
+        if os.path.exists(dest_file):
+            continue
         print '%s -> %s' % (library_path, dest_file)
         pull_cmd = [ADB_PATH, 'pull', library_path, dest_file]
         subprocess.check_call(pull_cmd, stderr=dev_null)
diff --git a/tools/skydb b/tools/skydb
index e99509d762c849ddd4424a4e3ab572c837b603c9..1a5285560379d5c1d481eba4a4842634770ab0b6 100755
--- a/tools/skydb
+++ b/tools/skydb
@@ -37,7 +37,8 @@ ANDROID_APK_NAME = 'MojoShell.apk'
 
 PID_FILE_PATH = "/tmp/skydb.pids"
 CACHE_LINKS_PATH = '/tmp/mojo_cache_links'
-SYSTEM_LIBS_ROOT_PATH = '/tmp/device_libs'
+# TODO(iansf): Fix undefined behavior when you have more than one device attached.
+SYSTEM_LIBS_ROOT_PATH = '/tmp/device_libs/%s' % (subprocess.check_output(['adb', 'get-serialno']).strip())
 
 SRC_ROOT = skypy.paths.Paths('ignored').src_root
 ADB_PATH = os.path.join(SRC_ROOT,