diff --git a/src/framebufferseries.cpp b/src/framebufferseries.cpp
--- a/src/framebufferseries.cpp
+++ b/src/framebufferseries.cpp
@@ -27,7 +27,7 @@ FrameBufferSeries::FrameBufferSeries(Fra
     _xmax = 1;
     _buffer = buffer;
     int_index_start = 0;
-    int_index_end = 0;
+    int_index_end = _buffer->size();
 }
 
 void FrameBufferSeries::setXAxis(bool asIndex, double xmin, double xmax)
@@ -85,6 +85,6 @@ void FrameBufferSeries::setRectOfInteres
         int_index_end = ceil(bsize * (rect.right()-_xmin) / xsize)+1;
     }
 
-    int_index_start = std::max(int_index_start, (size_t) 0);
-    int_index_end = std::min(_buffer->size(), int_index_end);
+    int_index_start = std::max(int_index_start, 0);
+    int_index_end = std::min((int) _buffer->size(), int_index_end);
 }
diff --git a/src/framebufferseries.h b/src/framebufferseries.h
--- a/src/framebufferseries.h
+++ b/src/framebufferseries.h
@@ -52,8 +52,8 @@ private:
     double _xmin;
     double _xmax;
 
-    size_t int_index_start; ///< starting index of "rectangle of interest"
-    size_t int_index_end;   ///< ending index of "rectangle of interest"
+    int int_index_start; ///< starting index of "rectangle of interest"
+    int int_index_end;   ///< ending index of "rectangle of interest"
 };
 
 #endif // FRAMEBUFFERSERIES_H