diff --git a/ChangeLog b/ChangeLog
index 33aca81302..5d2cff9a5a 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+2021-05-06  6.9.12-12  <quetzlzacatenango@image...>
+  * Release ImageMagick version 6.9.12-11 GIT revision 16...
+
+2021-05-06  6.9.12-12  <quetzlzacatenango@image...>
+  * -layers optimize no longer produces broken output (reference
+    https://github.com/ImageMagick/ImageMagick/issues/3520).
+
 2021-05-04  6.9.12-11  <quetzlzacatenango@image...>
   * Release ImageMagick version 6.9.12-11 GIT revision 16625:7d8a3b762:20210504
 
@@ -23,8 +30,6 @@
 
 2021-04-09  6.9.12-8  <quetzlzacatenango@image...>
   * constrain sub-image list.
-  * -layers optimize no longer produces broken output (reference
-    https://github.com/ImageMagick/ImageMagick/issues/3520).
   * write tiff colormapped images with an alpha channel as PHOTOMETRIC_RGB
 
 2021-04-03  6.9.12-6  <quetzlzacatenango@image...>
diff --git a/magick/quantize.c b/magick/quantize.c
index 1f2957f5e7..ce409353aa 100644
--- a/magick/quantize.c
+++ b/magick/quantize.c
@@ -1784,11 +1784,11 @@ static MagickBooleanType RiemersmaDither(Image *image,CacheView *image_view,
       AssociateAlphaPixel(cube_info,q,&pixel);
       for (i=0; i < ErrorQueueLength; i++)
       {
-        pixel.red+=p->weights[i]*p->error[i].red;
-        pixel.green+=p->weights[i]*p->error[i].green;
-        pixel.blue+=p->weights[i]*p->error[i].blue;
+        pixel.red+=p->weights[i]*p->error[i].red/16;
+        pixel.green+=p->weights[i]*p->error[i].green/16;
+        pixel.blue+=p->weights[i]*p->error[i].blue/16;
         if (cube_info->associate_alpha != MagickFalse)
-          pixel.opacity+=p->weights[i]*p->error[i].opacity;
+          pixel.opacity+=p->weights[i]*p->error[i].opacity/16;
       }
       pixel.red=(MagickRealType) ClampPixel(pixel.red);
       pixel.green=(MagickRealType) ClampPixel(pixel.green);
@@ -1993,7 +1993,7 @@ static CubeInfo *GetCubeInfo(const QuantizeInfo *quantize_info,
   for (i=0; i < ErrorQueueLength; i++)
   {
     cube_info->weights[ErrorQueueLength-i-1]=PerceptibleReciprocal(weight);
-    weight*=exp(log(((double) QuantumRange+1.0))/(ErrorQueueLength-1.0));
+    weight*=exp(log(16)/(ErrorQueueLength-1.0));
   }
   /*
     Normalize the weighting factors.