diff --git a/src/framebuffer.h b/src/framebuffer.h
--- a/src/framebuffer.h
+++ b/src/framebuffer.h
@@ -20,11 +20,10 @@
 #ifndef FRAMEBUFFER_H
 #define FRAMEBUFFER_H
 
-#include <qwt_series_data.h>
 #include <QPointF>
 #include <QRectF>
 
-class FrameBuffer : public QwtSeriesData<QPointF>
+class FrameBuffer
 {
 public:
     FrameBuffer(size_t size);
@@ -34,10 +33,10 @@ public:
     void addSamples(double* samples, size_t size);
     void clear(); // fill 0
 
-    // QwtSeriesData implementations
+    // QwtSeriesData related implementations
     size_t size() const;
-    QPointF sample(size_t i) const;
     QRectF boundingRect() const;
+    double sample(size_t i) const;
 
 private:
     size_t _size; // size of `data`
@@ -45,8 +44,6 @@ private:
     size_t headIndex; // indicates the actual `0` index of the ring buffer
 
     QRectF _boundingRect;
-
-    double _sample(size_t i) const;
 };
 
 #endif // FRAMEBUFFER_H