diff --git a/src/hb-buffer.cc b/src/hb-buffer.cc
index 13fe11f18..0632a4abb 100644
--- a/src/hb-buffer.cc
+++ b/src/hb-buffer.cc
@@ -1755,6 +1755,21 @@ hb_buffer_append (hb_buffer_t *buffer,
   memcpy (buffer->info + orig_len, source->info + start, (end - start) * sizeof (buffer->info[0]));
   if (buffer->have_positions)
     memcpy (buffer->pos + orig_len, source->pos + start, (end - start) * sizeof (buffer->pos[0]));
+
+  if (source->content_type == HB_BUFFER_CONTENT_TYPE_UNICODE)
+  {
+    /* pre-context */
+    while (start > 0 && buffer->context_len[0] < buffer->CONTEXT_LENGTH)
+      buffer->context[0][buffer->context_len[0]++] = source->info[--start].codepoint;
+    for (auto i = 0u; i < source->context_len[0] && buffer->context_len[0] < buffer->CONTEXT_LENGTH; i++)
+      buffer->context[0][buffer->context_len[0]++] = source->context[0][i];
+
+    /* post-context */
+    while (end < source->len && buffer->context_len[1] < buffer->CONTEXT_LENGTH)
+      buffer->context[1][buffer->context_len[1]++] = source->info[end++].codepoint;
+    for (auto i = 0u; i < source->context_len[1] && buffer->context_len[1] < buffer->CONTEXT_LENGTH; i++)
+      buffer->context[1][buffer->context_len[1]++] = source->context[1][i];
+  }
 }
 
 
diff --git a/util/shape-options.hh b/util/shape-options.hh
index 89dd8dfc9..a87c9d48c 100644
--- a/util/shape-options.hh
+++ b/util/shape-options.hh
@@ -235,7 +235,6 @@ struct shape_options_t
       hb_buffer_clear_contents (fragment);
       copy_buffer_properties (fragment, buffer);
 
-      /* TODO: Add pre/post context text. */
       hb_buffer_flags_t flags = hb_buffer_get_flags (fragment);
       if (0 < text_start)
 	flags = (hb_buffer_flags_t) (flags & ~HB_BUFFER_FLAG_BOT);