diff --git a/ChangeLog b/ChangeLog
index afe63fc84..2f05d8e58 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,16 @@
+2017-11-01  Alexei Podtelezhnikov  <apodtele@gmail.com>
+
+	[smooth] Fix complex rendering at high ppem.
+
+	We used to split large glyphs into horizontal bands and continue
+	bisecting them still horizontally if that was not enough.  This is
+	guaranteed to fail when a single scanline cannot fit into the
+	rendering memory pool.  Now we bisect the bands vertically so that
+	the smallest unit is a column of the band height, which is guranteed
+	to fit into memory.
+
+	* src/smooth/ftgrays.c (gray_convert_glyph): Implement it.
+
 2017-10-20  Alexei Podtelezhnikov  <apodtele@gmail.com>
 
 	[smooth] Improve complex rendering at high ppem.
diff --git a/src/smooth/ftgrays.c b/src/smooth/ftgrays.c
index fa488ecb9..91ca6e339 100644
--- a/src/smooth/ftgrays.c
+++ b/src/smooth/ftgrays.c
@@ -1736,35 +1736,43 @@ typedef ptrdiff_t  FT_PtrDist;
   static int
   gray_convert_glyph( RAS_ARG )
   {
+    const TCoord  yMin = ras.min_ey;
+    const TCoord  yMax = ras.max_ey;
+    const TCoord  xMin = ras.min_ex;
+    const TCoord  xMax = ras.max_ex;
+
     TCell    buffer[FT_MAX_GRAY_POOL];
-    TCoord   band_size = FT_MAX_GRAY_POOL / 8;
-    TCoord   count = ras.max_ey - ras.min_ey;
-    int      num_bands;
-    TCoord   min, max, max_y;
+    size_t   height = (size_t)( yMax - yMin );
+    size_t   n = FT_MAX_GRAY_POOL / 8;
+    TCoord   y;
     TCoord   bands[32];  /* enough to accommodate bisections */
     TCoord*  band;
 
 
     /* set up vertical bands */
-    if ( count > band_size )
+    if ( height > n )
     {
       /* two divisions rounded up */
-      num_bands = (int)( ( count + band_size - 1) / band_size );
-      band_size = ( count + num_bands - 1 ) / num_bands;
+      n       = ( height + n - 1 ) / n;
+      height  = ( height + n - 1 ) / n;
     }
 
-    min   = ras.min_ey;
-    max_y = ras.max_ey;
+    /* memory management */
+    n = ( height * sizeof ( PCell ) + sizeof ( TCell ) - 1 ) / sizeof ( TCell );
+
+    ras.cells     = buffer + n;
+    ras.max_cells = (FT_PtrDist)( FT_MAX_GRAY_POOL - n );
+    ras.ycells    = (PCell*)buffer;
 
-    for ( ; min < max_y; min = max )
+    for ( y = yMin; y < yMax; )
     {
-      max = min + band_size;
-      if ( max > max_y )
-        max = max_y;
+      ras.min_ey = y;
+      y         += height;
+      ras.max_ey = FT_MIN( y, yMax );
 
       band    = bands;
-      band[1] = min;
-      band[0] = max;
+      band[1] = xMin;
+      band[0] = xMax;
 
       do
       {
@@ -1772,27 +1780,12 @@ typedef ptrdiff_t  FT_PtrDist;
         int     error;
 
 
-        /* memory management */
-        {
-          size_t  ycount = (size_t)width;
-          size_t  cell_start;
-
-
-          cell_start = ( ycount * sizeof ( PCell ) + sizeof ( TCell ) - 1 ) /
-                       sizeof ( TCell );
-
-          ras.cells     = buffer + cell_start;
-          ras.max_cells = (FT_PtrDist)( FT_MAX_GRAY_POOL - cell_start );
-          ras.num_cells = 0;
-
-          ras.ycells = (PCell*)buffer;
-          while ( ycount )
-            ras.ycells[--ycount] = NULL;
-        }
+        FT_MEM_ZERO( ras.ycells, height * sizeof ( PCell ) );
 
+        ras.num_cells = 0;
         ras.invalid   = 1;
-        ras.min_ey    = band[1];
-        ras.max_ey    = band[0];
+        ras.min_ex    = band[1];
+        ras.max_ex    = band[0];
 
         error = gray_convert_glyph_inner( RAS_VAR );
 
@@ -1808,8 +1801,7 @@ typedef ptrdiff_t  FT_PtrDist;
         /* render pool overflow; we will reduce the render band by half */
         width >>= 1;
 
-        /* This is too complex for a single scanline; there must */
-        /* be some problems.                                     */
+        /* this should never happen even with tiny rendering pool */
         if ( width == 0 )
         {
           FT_TRACE7(( "gray_convert_glyph: rotten glyph\n" ));