NoClassDefFoundError on Calligraphy library

Question

After adding compile 'com.android.support:support-v13:21.0.+' to build.gradle, I had some conflicts on building my app, so I had to add multiDexEnabled = true to defaultConfig inside build.gradle. Those conflict are gone, but i got another exception (on opening the app) for the missing calligraphy library:

java.lang.NoClassDefFoundError: uk.co.chrisjenx.calligraphy.R$attr
        at uk.co.chrisjenx.calligraphy.CalligraphyConfig$Builder.<init>(CalligraphyConfig.java:150)
        at com.taxiyaab.android.util.ApplicationClass.onCreate(ApplicationClass.java:120)
        at newapp.com.taxiyaab.taxiyaab.PassengerApplication.onCreate(PassengerApplication.java:68)
        at android.app.Instrumentation.callApplicationOnCreate(Instrumentation.java:1007)
        at android.app.ActivityThread.handleBindApplication(ActivityThread.java:4462)
        at android.app.ActivityThread.access$1500(ActivityThread.java:144)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1306)
        at android.os.Handler.dispatchMessage(Handler.java:102)
        at android.os.Looper.loop(Looper.java:212)
        at android.app.ActivityThread.main(ActivityThread.java:5135)
        at java.lang.reflect.Method.invokeNative(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:515)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:878)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
        at dalvik.system.NativeStart.main(Native Method)

My latest sdk build tools version is 22.0.1. Has anybody faced this issue before?