diff --git a/src/libOpenImageIO/imageinput.cpp b/src/libOpenImageIO/imageinput.cpp
index f63ab45de1..3ec308b0d2 100644
--- a/src/libOpenImageIO/imageinput.cpp
+++ b/src/libOpenImageIO/imageinput.cpp
@@ -232,8 +232,8 @@ ImageInput::read_scanlines (int ybegin, int yend, int z,
                 TypeDesc chanformat = m_spec.channelformats[c+firstchan];
                 ok = convert_image (1 /* channels */, m_spec.width, nscanlines, 1, 
                                     &buf[offset], chanformat, 
-                                    pixel_bytes, AutoStride, AutoStride,
-                                    (char *)data + c*m_spec.format.size(),
+                                    native_pixel_bytes, native_scanline_bytes, 0,
+                                    (char *)data + c*format.size(),
                                     format, xstride, ystride, zstride);
                 offset += chanformat.size ();
             }
@@ -444,6 +444,9 @@ ImageInput::read_tiles (int xbegin, int xend, int ybegin, int yend,
                                      : (format.size() * nchans);
     stride_t full_pixelsize = native_data ? m_spec.pixel_bytes(true)
                                           : (format.size() * m_spec.nchannels);
+    stride_t full_tilewidthbytes = full_pixelsize * m_spec.tile_width;
+    stride_t full_tilewhbytes = full_tilewidthbytes * m_spec.tile_height;
+    stride_t full_tilebytes = full_tilewhbytes * m_spec.tile_depth;
     size_t prefix_bytes = m_spec.pixel_bytes (0,firstchan,true);
     std::vector<char> buf;
     for (int z = zbegin;  z < zend;  z += std::max(1,m_spec.tile_depth)) {
@@ -464,16 +467,14 @@ ImageInput::read_tiles (int xbegin, int xend, int ybegin, int yend,
                     ok &= read_tile (x, y, z, format, tilestart,
                                      xstride, ystride, zstride);
                 } else {
-                    buf.resize (m_spec.tile_bytes());
+                    buf.resize (full_tilebytes);
                     ok &= read_tile (x, y, z, format, &buf[0],
-                                     full_pixelsize,
-                                     full_pixelsize*m_spec.tile_width,
-                                     full_pixelsize*m_spec.tile_pixels());
+                                     full_pixelsize, full_tilewidthbytes,
+                                     full_tilewhbytes);
                     if (ok)
                         copy_image (nchans, xw, yh, zd, &buf[prefix_bytes],
                                     pixelsize, full_pixelsize,
-                                    full_pixelsize*m_spec.tile_width,
-                                    full_pixelsize*m_spec.tile_pixels(),
+                                    full_tilewidthbytes, full_tilewhbytes,
                                     tilestart, xstride, ystride, zstride);
                 }
                 tilestart += m_spec.tile_width * xstride;
diff --git a/src/libtexture/imagecache.cpp b/src/libtexture/imagecache.cpp
index f25217039a..f4fead0190 100644
--- a/src/libtexture/imagecache.cpp
+++ b/src/libtexture/imagecache.cpp
@@ -415,6 +415,8 @@ ImageCacheFile::open (ImageCachePerThreadInfo *thread_info)
                 invalidate_spec ();
                 return false;
             }
+            // ImageCache can't store differing formats per channel
+            tempspec.channelformats.clear();
             LevelInfo levelinfo (tempspec, nativespec);
             si.levels.push_back (levelinfo);
             ++nmip;
diff --git a/testsuite/openexr-suite/ref/out.txt b/testsuite/openexr-suite/ref/out.txt
index 463b637981..75b3da2975 100644
--- a/testsuite/openexr-suite/ref/out.txt
+++ b/testsuite/openexr-suite/ref/out.txt
@@ -66,7 +66,7 @@ Comparing "../../../../../openexr-images-1.5.0/ScanLines/Tree.exr" and "Tree.exr
 PASS
 Reading ../../../../../openexr-images-1.5.0/ScanLines/Blobbies.exr
 ../../../../../openexr-images-1.5.0/ScanLines/Blobbies.exr : 1040 x 1040, 5 channel, half/half/half/half/float openexr
-    SHA-1: 1D3D059692BB2074264393AA2B04D3E60DC52BDC
+    SHA-1: 64C3C765E0D40AA92E066F6EC9198A8053BF1179
     channel list: R (half), G (half), B (half), A (half), Z (float)
     pixel data origin: x=-20, y=-20
     full/display size: 1000 x 1000