Untiy3D 4.5 bind to fbo failed in OnPreRender

public class Test : MonoBehaviour {
[DllImport (“test”)]
private static extern int testOnPreRender();
[DllImport (“test”)]
private static extern int testOnPostRender();

	void OnPreRender() {
		testOnPreRender()
	}
	
	void OnPostRender() {
		testOnPostRender();
	}
}

int testOnPreRender()
{
	LOGD("glBindFramebuffer %d", myFBO); // print 3
	glBindFramebuffer(GL_FRAMEBUFFER, myFBO)
	GLuint fbo = 0;
	glGetIntegerv(GL_FRAMEBUFFER_BINDING, (GLint *)&fbo);
	LOGD("glBindFramebufferFB=%d.", fbo); // print 3	
}

int testOnPostRender()
{
	GLuint fbo = 0;
	glGetIntegerv(GL_FRAMEBUFFER_BINDING, (GLint *)&fbo);
	LOGD("glBindFramebufferFB=%d.", fbo); // print 0 in unity4.5+, print 3 in unity4.2+ 4.3+ 4.4+
}

Hi, everyone! The code is work OK with Sumsung S4 in Unity3D 4.2+, 4.3+, 4.4+, but failed with Unity3D4.5+ ! I want to bind to offscreen fbo in testOnPreRender, but testOnPostRender print fbo is 0! Is it betwwen OnPreRender() and OnPostRender() has call glBindFramebuffer(GL_FRAMEBUFFER, 0) in Unity4.5? if so, how to bind to my fbo in Unity3D4.5+?

unity will clear most flags before rendering each frame, including glBindFramebuffer(GL_FRAMEBUFFER, 0).