diff --git a/common/rfb/ScaleFilters.cxx b/common/rfb/ScaleFilters.cxx
index 50b9bd9..a3ee53e 100644
--- a/common/rfb/ScaleFilters.cxx
+++ b/common/rfb/ScaleFilters.cxx
@@ -95,6 +95,8 @@
   double sxc;
   double offset = 0.5;
   double ratio = (double)dst_x / src_x;
+  double sourceScale  = __rfbmax(1.0, 1.0/ratio);
+  double sourceRadius = __rfbmax(0.5, sourceScale * filters[filter_id].radius);
   double sum, nc;
   int i, ci;
 
@@ -108,20 +110,20 @@
     sxc = (double(x)+offset) / ratio;
 
     // Calculate the scale filter interval, [i0, i1)
-    int i0 = int(__rfbmax(sxc-sFilter.radius+0.5, 0));
-    int i1 = int(__rfbmin(sxc+sFilter.radius+0.5, src_x));
+    int i0 = int(__rfbmax(sxc-sourceRadius+0.5, 0));
+    int i1 = int(__rfbmin(sxc+sourceRadius+0.5, src_x));
 
     weightTabs[x].i0 = i0; weightTabs[x].i1 = i1;
     weightTabs[x].weight = new short[i1-i0];
 
     // Calculate coeff to normalize the filter weights
-    for (sum = 0, i = i0; i < i1; i++) sum += sFilter.func(double(i)-sxc+0.5);
+    for (sum = 0, i = i0; i < i1; i++) sum += sFilter.func((double(i)-sxc+0.5)/sourceScale);
     if (sum == 0.) nc = (double)(WEIGHT_OF_ONE); else nc = (double)(WEIGHT_OF_ONE)/sum;
 
 
     // Calculate the weight coeffs on the scale filter interval
     for (ci = 0, i = i0; i < i1; i++) {
-      weightTabs[x].weight[ci++] = (short)floor((sFilter.func(double(i)-sxc+0.5) * nc) + 0.5);
+      weightTabs[x].weight[ci++] = (short)floor((sFilter.func((double(i)-sxc+0.5)/sourceScale) * nc) + 0.5);
     }
   }
 }
diff --git a/common/rfb/ScaleFilters.h b/common/rfb/ScaleFilters.h
index 0a8c482..570dc51 100644
--- a/common/rfb/ScaleFilters.h
+++ b/common/rfb/ScaleFilters.h
@@ -24,6 +24,7 @@
 
 namespace rfb {
 
+  #define SCALE_ERROR 1e-7
   #define BITS_OF_CHANEL 8
   #define BITS_OF_WEIGHT 14
   #define FINALSHIFT 2 * BITS_OF_WEIGHT - BITS_OF_CHANEL
diff --git a/common/rfb/ScaledPixelBuffer.cxx b/common/rfb/ScaledPixelBuffer.cxx
index 5b6e310..12658f7 100644
--- a/common/rfb/ScaledPixelBuffer.cxx
+++ b/common/rfb/ScaledPixelBuffer.cxx
@@ -94,8 +94,8 @@
 
 void ScaledPixelBuffer::setScale(int scale_) {
   if (scale != scale_ && scale_ > 0) {
-    freeWeightTabs();
     scale = scale_;
+    freeWeightTabs();
     calculateScaledBufferSize();
     scaleFilters.makeWeightTabs(scaleFilterID, src_width, scaled_width, &xWeightTabs);
     scaleFilters.makeWeightTabs(scaleFilterID, src_height, scaled_height, &yWeightTabs);
@@ -204,13 +204,16 @@
 
 Rect ScaledPixelBuffer::calculateScaleBoundary(const Rect& r) {
   int x_start, y_start, x_end, y_end;
-  double radius = scaleFilters[scaleFilterID].radius;
   double translate_x = 0.5*scale_ratio_x - 0.5;
   double translate_y = 0.5*scale_ratio_y - 0.5;
-  x_start = (int)ceil(scale_ratio_x*(r.tl.x-radius) + translate_x);
-  y_start = (int)ceil(scale_ratio_y*(r.tl.y-radius) + translate_y);
-  x_end = (int)ceil(scale_ratio_x*(r.br.x+radius) + translate_x);
-  y_end = (int)ceil(scale_ratio_y*(r.br.y+radius) + translate_y);
+  double sourceXScale  = __rfbmax(1.0, 1.0/scale_ratio_x);
+  double sourceYScale  = __rfbmax(1.0, 1.0/scale_ratio_y);
+  double sourceXRadius = __rfbmax(0.5, sourceXScale*scaleFilters[scaleFilterID].radius);
+  double sourceYRadius = __rfbmax(0.5, sourceYScale*scaleFilters[scaleFilterID].radius);
+  x_start = (int)ceil(scale_ratio_x*(r.tl.x-sourceXRadius) + translate_x + SCALE_ERROR);
+  y_start = (int)ceil(scale_ratio_y*(r.tl.y-sourceYRadius) + translate_y + SCALE_ERROR);
+  x_end   = (int)floor(scale_ratio_x*((r.br.x-1)+sourceXRadius) + translate_x - SCALE_ERROR) + 1;
+  y_end   = (int)floor(scale_ratio_y*((r.br.y-1)+sourceXRadius) + translate_y - SCALE_ERROR) + 1;
   if (x_start < 0) x_start = 0;
   if (y_start < 0) y_start = 0;
   if (x_end > scaled_width) x_end = scaled_width;