diff --git a/src/hb-buffer-serialize.cc b/src/hb-buffer-serialize.cc
index bac43a33a..d9e9e7bc0 100644
--- a/src/hb-buffer-serialize.cc
+++ b/src/hb-buffer-serialize.cc
@@ -592,6 +592,35 @@ hb_buffer_serialize_unicode (hb_buffer_t *buffer,
 
   }
 }
+
+static unsigned int
+_hb_buffer_serialize_invalid (hb_buffer_t *buffer,
+                              unsigned int start,
+                              unsigned int end,
+                              char *buf,
+                              unsigned int buf_size,
+                              unsigned int *buf_consumed,
+                              hb_buffer_serialize_format_t format,
+                              hb_buffer_serialize_flags_t flags)
+{
+  unsigned int sconsumed;
+  if (!buf_consumed)
+    buf_consumed = &sconsumed;
+  if (buf_size < 3)
+    return 0;
+  if (format == HB_BUFFER_SERIALIZE_FORMAT_JSON) {
+    *buf++ = '[';
+    *buf++ = ']';
+    *buf = '\0';
+  } else if (format == HB_BUFFER_SERIALIZE_FORMAT_TEXT) {
+    *buf++ = '!';
+    *buf++ = '!';
+    *buf = '\0';
+  }
+  *buf_consumed = 2;
+  return 0;
+}
+
 /**
  * hb_buffer_serialize:
  * @buffer: an #hb_buffer_t buffer.
@@ -629,12 +658,22 @@ hb_buffer_serialize (hb_buffer_t *buffer,
                      hb_buffer_serialize_format_t format,
                      hb_buffer_serialize_flags_t flags)
 {
-  if (buffer->content_type == HB_BUFFER_CONTENT_TYPE_GLYPHS)
-    return hb_buffer_serialize_glyphs(buffer, start, end, buf, buf_size,
-                                      buf_consumed, font, format, flags);
-  else
-    return hb_buffer_serialize_unicode(buffer, start, end, buf, buf_size,
+  switch (buffer->content_type)
+  {
+
+    case HB_BUFFER_CONTENT_TYPE_GLYPHS:
+      return hb_buffer_serialize_glyphs(buffer, start, end, buf, buf_size,
+                                        buf_consumed, font, format, flags);
+
+    case HB_BUFFER_CONTENT_TYPE_UNICODE:
+      return hb_buffer_serialize_unicode(buffer, start, end, buf, buf_size,
                                        buf_consumed, format, flags);
+
+    case HB_BUFFER_CONTENT_TYPE_INVALID:
+    default:
+      return _hb_buffer_serialize_invalid(buffer, start, end, buf, buf_size,
+                                           buf_consumed, format, flags);
+  }
 }
 
 static bool
diff --git a/test/api/test-buffer.c b/test/api/test-buffer.c
index b3cd1bf40..6904b36bb 100644
--- a/test/api/test-buffer.c
+++ b/test/api/test-buffer.c
@@ -898,14 +898,28 @@ test_buffer_serialize_deserialize (void)
 		num_glyphs = hb_buffer_get_length (b);
 		g_assert_cmpint (num_glyphs, ==, test->num_items);
 
-		hb_buffer_serialize_unicode(b, 0, num_glyphs, round_trip,
-																sizeof(round_trip), &consumed, test->format,
-																HB_BUFFER_SERIALIZE_FLAG_DEFAULT);
+		hb_buffer_serialize_unicode (b, 0, num_glyphs, round_trip,
+																 sizeof(round_trip), &consumed, test->format,
+																 HB_BUFFER_SERIALIZE_FLAG_DEFAULT);
 		g_assert_cmpstr (round_trip, ==, test->contents);
 
 		hb_buffer_destroy (b);
 
 	}
+
+  char test[1024];
+  unsigned int num_glyphs, consumed;
+  hb_buffer_t *indeterminate = hb_buffer_get_empty ();
+  hb_buffer_serialize (indeterminate, 0, hb_buffer_get_length (indeterminate),
+    test, sizeof(test), &consumed, NULL, HB_BUFFER_SERIALIZE_FORMAT_JSON,
+    HB_BUFFER_SERIALIZE_FLAG_DEFAULT);
+  g_assert_cmpstr ( test, ==, "[]");
+
+  hb_buffer_serialize (indeterminate, 0, hb_buffer_get_length (indeterminate),
+    test, sizeof(test), &consumed, NULL, HB_BUFFER_SERIALIZE_FORMAT_TEXT,
+    HB_BUFFER_SERIALIZE_FLAG_DEFAULT);
+  g_assert_cmpstr ( test, ==, "!!");
+
 }
 
 int