diff --git a/plugins/audio_file_processor/audio_file_processor.cpp b/plugins/audio_file_processor/audio_file_processor.cpp
index 729e9e429..5520c7302 100644
--- a/plugins/audio_file_processor/audio_file_processor.cpp
+++ b/plugins/audio_file_processor/audio_file_processor.cpp
@@ -932,8 +932,12 @@ void AudioFileProcessorWaveView::slideSampleByFrames( f_cnt_t _frames )
 		return;
 	}
 	const double v = double( _frames ) / m_sampleBuffer.frames();
-	m_startKnob->slideBy( v, false );
-	m_endKnob->slideBy( v, false );
+	if(m_startKnob) {
+		m_startKnob->slideBy( v, false );
+	}
+	if(m_endKnob) {
+		m_endKnob->slideBy( v, false );
+	}
 }