android.support.v7.appcompat,java.lang.NoSuchFieldError: android.support.v7.appcompat

I updated my support library from r20 to r21, now when I run my app I get this error in super.onCreate of my main activity :

java.lang.NoSuchFieldError: android.support.v7.appcompat.R$styleable.Theme_windowActionBar

at android.support.v7.app.ActionBarActivityDelegate.onCreate(ActionBarActivityDelegate.java:145)

at android.support.v7.app.ActionBarActivityDelegateBase.onCreate(ActionBarActivityDelegateBase.java:139)

at android.support.v7.app.ActionBarActivity.onCreate(ActionBarActivity.java:123)

at (packageName).Main.onCreate(Main.java:64)

at android.app.Activity.performCreate(Activity.java)

at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java)

at android.app.ActivityThread.performLaunchActivity(ActivityThread.java)

at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java)

at android.app.ActivityThread.access$700(ActivityThread.java)

at android.app.ActivityThread$H.handleMessage(ActivityThread.java)

at android.os.Handler.dispatchMessage(Handler.java)

at android.os.Looper.loop(Looper.java)

at android.app.ActivityThread.main(ActivityThread.java)

at java.lang.reflect.Method.invokeNative(Native Method)

at java.lang.reflect.Method.invoke(Method.java)

at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java)

at com.android.internal.os.ZygoteInit.main(ZygoteInit.java)

at dalvik.system.NativeStart.main(Native Method)

my theme.xml :

...

in manifest :

android:theme="@style/AppTheme"

what is the problem ?

thanks