--- a/gfx/src/FilterSupport.cpp
+++ b/gfx/src/FilterSupport.cpp
@@ -2,16 +2,17 @@
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 #include "FilterSupport.h"
 
 #include "mozilla/gfx/2D.h"
 #include "mozilla/gfx/Filters.h"
+#include "mozilla/gfx/Logging.h"
 #include "mozilla/PodOperations.h"
 
 #include "gfxContext.h"
 #include "gfxPattern.h"
 #include "gfxPlatform.h"
 #include "gfx2DGlue.h"
 
 #include "nsMargin.h"
@@ -394,18 +395,19 @@ ComputeColorMatrix(uint32_t aColorMatrix
   static const float hueRotateR = 0.143f;
   static const float hueRotateG = 0.140f;
   static const float hueRotateB = 0.283f;
 
   switch (aColorMatrixType) {
 
     case SVG_FECOLORMATRIX_TYPE_MATRIX:
     {
-      if (aValues.Length() != 20)
+      if (aValues.Length() != 20) {
         return NS_ERROR_FAILURE;
+      }
 
       PodCopy(aOutMatrix, aValues.Elements(), 20);
       break;
     }
 
     case SVG_FECOLORMATRIX_TYPE_SATURATE:
     {
       if (aValues.Length() != 1)
@@ -1474,17 +1476,17 @@ FilterSupport::PostFilterExtentsForPrimi
       }
       return ThebesIntRect(aDescription.PrimitiveSubregion());
     }
 
     case PrimitiveType::ColorMatrix:
     {
       if (atts.GetUint(eColorMatrixType) == (uint32_t)SVG_FECOLORMATRIX_TYPE_MATRIX) {
         const nsTArray<float>& values = atts.GetFloats(eColorMatrixValues);
-        if (values[19] > 0.0f) {
+        if (values.Length() == 20 && values[19] > 0.0f) {
           return ThebesIntRect(aDescription.PrimitiveSubregion());
         }
       }
       return aInputExtents[0];
     }
 
     case PrimitiveType::ComponentTransfer:
     {