Blend Filter problem.

I was using GPUImage framework (some old version) to blend 2 images (add border overlay to certain image).
After I have updated to new framework, after applying such a blend, I get empty black image.

I'm using next method:

- (void)addBorder {
if (currentBorder != kBorderInitialValue) {
GPUImageAlphaBlendFilter *blendFilter = [[GPUImageAlphaBlendFilter alloc] init];
GPUImagePicture *imageToProcess = [[GPUImagePicture alloc] initWithImage:self.imageToWorkWithView.image];
GPUImagePicture *border = [[GPUImagePicture alloc] initWithImage:self.imageBorder];

blendFilter.mix = 1.0f;
[imageToProcess addTarget:blendFilter];
[border addTarget:blendFilter];

[imageToProcess processImage];
self.imageToWorkWithView.image = [blendFilter imageFromCurrentlyProcessedOutput];

[blendFilter release];
[imageToProcess release];
[border release];
}
}

What is the problem?