diff --git a/src/codec/SkJpegCodec.cpp b/src/codec/SkJpegCodec.cpp
index c883b3e..a60e9f8 100644
--- a/src/codec/SkJpegCodec.cpp
+++ b/src/codec/SkJpegCodec.cpp
@@ -831,15 +831,13 @@
     }
 
     jpeg_component_info * comp_info = dinfo->comp_info;
-    for (auto i : { SkYUVAIndex::kY_Index, SkYUVAIndex::kU_Index, SkYUVAIndex::kV_Index }) {
+    for (int i = 0; i < 3; ++i) {
         sizeInfo->fSizes[i].set(comp_info[i].downsampled_width, comp_info[i].downsampled_height);
         sizeInfo->fWidthBytes[i] = comp_info[i].width_in_blocks * DCTSIZE;
     }
 
     // JPEG never has an alpha channel
-    sizeInfo->fSizes[SkYUVAIndex::kA_Index].fHeight =
-        sizeInfo->fSizes[SkYUVAIndex::kA_Index].fWidth =
-        sizeInfo->fWidthBytes[SkYUVAIndex::kA_Index] = 0;
+    sizeInfo->fSizes[3].fHeight = sizeInfo->fSizes[3].fWidth = sizeInfo->fWidthBytes[3] = 0;
 
     if (colorSpace) {
         *colorSpace = kJPEG_SkYUVColorSpace;
diff --git a/src/core/SkImageGenerator.cpp b/src/core/SkImageGenerator.cpp
index 2c59c9a..1f16bc8 100644
--- a/src/core/SkImageGenerator.cpp
+++ b/src/core/SkImageGenerator.cpp
@@ -62,7 +62,7 @@
                     yuvaIndices[SkYUVAIndex::kA_Index].fChannel = SkColorChannel::kR;
                     break;
                 case 2:
-                    // Assume 1 Y plane and interleaved UV planes (NV12)
+                    // Assume Y plane and interleaved UV plane (NV12)
                     yuvaIndices[SkYUVAIndex::kY_Index].fIndex = 0;
                     yuvaIndices[SkYUVAIndex::kY_Index].fChannel = SkColorChannel::kR;
                     yuvaIndices[SkYUVAIndex::kU_Index].fIndex = 1;
@@ -85,6 +85,8 @@
                     yuvaIndices[SkYUVAIndex::kA_Index].fChannel = SkColorChannel::kR;
                     break;
             }
+            // clear fourth element in sizeInfo to ensure it's initialized
+            sizeInfo->fSizes[3].fWidth = sizeInfo->fSizes[3].fHeight = sizeInfo->fWidthBytes[3] = 0;
 
             return true;
         }