Gradle无法解析otto库

我尝试嵌入位于Maven Central的Otto库.

buildscript {
    repositories {
        mavenCentral()
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:0.6.3'

    }
}

apply plugin: 'android'

dependencies {
    compile 'com.google.android.gms:play-services:4.0.30'
    compile 'com.android.support:support-v13:19.0.0'
    compile 'com.squareup:otto:1.3.4'
}

但是我得到了例外:

A problem occurred configuring root project 'sample-project'.
> Failed to notify project evaluation listener.
   > Could not resolve all dependencies for configuration ':_DebugCompile'.
      > Could not find com.squareup:otto:otto:1.3.4.
        Required by:
            :sample-project:unspecified

我试图刷新依赖项(gradle --refresh-dependencies)但它没有帮助.