diff --git a/Base/include/Image.h b/Base/include/Image.h
index 2550481..0b56aed 100644
--- a/Base/include/Image.h
+++ b/Base/include/Image.h
@@ -106,7 +106,7 @@ namespace FasTC {
     }
 
     double ComputePSNR(Image<PixelType> *other);
-    double ComputeSSIM(Image<PixelType> *other, double *mssim = 0);
+    double ComputeSSIM(Image<PixelType> *other);
     
     // Function to allow derived classes to populate the pixel array.
     // This may involve decompressing a compressed image or otherwise
diff --git a/Base/src/Image.cpp b/Base/src/Image.cpp
index 74a9fe7..c2c9d33 100644
--- a/Base/src/Image.cpp
+++ b/Base/src/Image.cpp
@@ -261,7 +261,7 @@ static Image<IPixel> FilterValid(const Image<IPixel> &img, uint32 size, double s
 }
 
 template<typename PixelType>
-double Image<PixelType>::ComputeSSIM(Image<PixelType> *other, double *mssim) {
+double Image<PixelType>::ComputeSSIM(Image<PixelType> *other) {
   if(!other) {
     return -1.0;
   }
@@ -384,11 +384,7 @@ double Image<PixelType>::ComputeSSIM(Image<PixelType> *other, double *mssim) {
     }
   }
 
-  double minSSIM = 1.0;
-  if(mssim) {
-    *mssim = 0.0;
-  }
-
+  double mssim = 0.0;
   for(uint32 j = 0; j < h; j++) {
     for(uint32 i = 0; i < w; i++) {
       double m1sq = static_cast<float>(mu1_sq(i, j));
@@ -403,19 +399,11 @@ double Image<PixelType>::ComputeSSIM(Image<PixelType> *other, double *mssim) {
         ((2.0 * m1m2 + C1) * (2.0 * s1s2 + C2)) /
         ((m1sq + m2sq + C1) * (s1sq + s2sq + C2));
 
-      if(mssim) {
-        *mssim += ssim;
-      }
-
-      minSSIM = ::std::min(ssim, minSSIM);
+      mssim += ssim;
     }
   }
 
-  if(mssim) {
-    *mssim /= static_cast<double>(w * h);
-  }
-
-  return minSSIM;
+  return mssim / static_cast<double>(w * h);
 }
 
 // !FIXME! These won't work for non-RGBA8 data.
diff --git a/Base/test/TestImage.cpp b/Base/test/TestImage.cpp
index f1c2a68..ff9d8d3 100644
--- a/Base/test/TestImage.cpp
+++ b/Base/test/TestImage.cpp
@@ -164,8 +164,6 @@ TEST(Image, ComputeMSSIM) {
     }
   }
 
-  double MSSIM;
-  double SSIM = img.ComputeSSIM(&img, &MSSIM);
+  double SSIM = img.ComputeSSIM(&img);
   EXPECT_EQ(SSIM, 1.0);
-  EXPECT_EQ(MSSIM, 1.0);
 }
diff --git a/CLTool/src/clunix.cpp b/CLTool/src/clunix.cpp
index 303e42b..a53f0f1 100644
--- a/CLTool/src/clunix.cpp
+++ b/CLTool/src/clunix.cpp
@@ -260,11 +260,9 @@ int main(int argc, char **argv) {
     fprintf(stderr, "Error computing PSNR\n");
   }
 
-  double MSSIM;
-  double SSIM = img.ComputeSSIM(ci, &MSSIM);
+  double SSIM = img.ComputeSSIM(ci);
   if(SSIM > 0.0) {
     fprintf(stdout, "SSIM: %.9f\n", SSIM);
-    fprintf(stdout, "MSSIM: %.9f\n", MSSIM);
   } else {
     fprintf(stderr, "Error computing MSSIM\n");
   }
diff --git a/CLTool/src/clwin32.cpp b/CLTool/src/clwin32.cpp
index a24418a..cb745c4 100644
--- a/CLTool/src/clwin32.cpp
+++ b/CLTool/src/clwin32.cpp
@@ -264,11 +264,9 @@ int _tmain(int argc, _TCHAR* argv[])
     fprintf(stderr, "Error computing PSNR\n");
   }
 
-  double MSSIM;
-  double SSIM = img.ComputeSSIM(ci, &MSSIM);
+  double SSIM = img.ComputeSSIM(ci);
   if(SSIM > 0.0) {
     fprintf(stdout, "SSIM: %.9f\n", SSIM);
-    fprintf(stdout, "MSSIM: %.9f\n", MSSIM);
   } else {
     fprintf(stderr, "Error computing MSSIM\n");
   }
diff --git a/CLTool/src/compare.cpp b/CLTool/src/compare.cpp
index 5e7d5d9..c439916 100644
--- a/CLTool/src/compare.cpp
+++ b/CLTool/src/compare.cpp
@@ -96,11 +96,9 @@ int main(int argc, char **argv) {
     fprintf(stderr, "Error computing PSNR\n");
   }
 
-  double MSSIM;
-  double SSIM = img1.ComputeSSIM(&img2, &MSSIM);
+  double SSIM = img1.ComputeSSIM(&img2);
   if(SSIM > 0.0) {
     fprintf(stdout, "SSIM: %.9f\n", SSIM);
-    fprintf(stdout, "MSSIM: %.9f\n", MSSIM);
   } else {
     fprintf(stderr, "Error computing MSSIM\n");
   }