diff --git a/Base/include/Image.h b/Base/include/Image.h
index a8c8fb3..cd81d9b 100644
--- a/Base/include/Image.h
+++ b/Base/include/Image.h
@@ -106,8 +106,8 @@ namespace FasTC {
     }
 
     double ComputePSNR(Image<PixelType> *other);
-    double ComputeMSSIM(Image<PixelType> *other) const;
-
+    double ComputeMSSIM(Image<PixelType> *other);
+    
     // Function to allow derived classes to populate the pixel array.
     // This may involve decompressing a compressed image or otherwise
     // processing some data in order to populate the m_Pixels pointer.
diff --git a/Base/src/Image.cpp b/Base/src/Image.cpp
index 3607216..de8f2ac 100644
--- a/Base/src/Image.cpp
+++ b/Base/src/Image.cpp
@@ -222,6 +222,7 @@ template<typename PixelType>
 static Image<PixelType> FilterValid(const Image<PixelType> &img, uint32 size, double sigma) {
   assert(size % 2);
   Image<IPixel> gaussian(size, size);
+  GenerateGaussianKernel(gaussian, size, sigma);
   Image<PixelType> tmp = img;
   tmp.Filter(gaussian);
 
@@ -237,7 +238,7 @@ static Image<PixelType> FilterValid(const Image<PixelType> &img, uint32 size, do
 }
 
 template<typename PixelType>
-double Image<PixelType>::ComputeMSSIM(Image<PixelType> *other) const {
+double Image<PixelType>::ComputeSSIM(Image<PixelType> *other) {
   if(!other) {
     return -1.0;
   }
@@ -247,6 +248,9 @@ double Image<PixelType>::ComputeMSSIM(Image<PixelType> *other) const {
     return -1.0;
   }
 
+  ComputePixels();
+  other->ComputePixels();
+
   double C1 = (0.01 * 255.0 * 0.01 * 255.0);
   double C2 = (0.03 * 255.0 * 0.03 * 255.0);