diff --git a/t/901-github-test-suite.t b/t/901-github-test-suite.t
index f1ea16f..c394f91 100644
--- a/t/901-github-test-suite.t
+++ b/t/901-github-test-suite.t
@@ -9,22 +9,26 @@ use CmarkTest;
 use Test2::V0;
 
 # TODO: remove these todos.
-my %opt = (todo => [198 .. 202, 204, 205, 398, 426, 434 .. 436,
-                       473 .. 475, 477, 629 .. 631, 652],
+my %opt = (todo => [198 .. 202, 204, 205, 629 .. 631, 652],
            # These are bugs in the GitHub spec, not in our implementation. All
            # of these have been tested to be buggy in the real cmark-gfm
            # implementation.
            bugs => [
-             # The spec says that some HTML tags are forbidden in the output, but
-             # they still have examples with these tags.
+             # The spec says that some HTML tags are forbidden in the output,
+             # but it still has examples with these tags.
             140 .. 142, 145, 147,
             # Some things that are not cmark autolinks are matched by the
             # extended autolinks syntax (but the cmark part of the spec is not
-            # updated).
+            # updated for it).
             616, 619,
-            # The spec says that only http:// and https:// scheme can be used
-            # for extended autolinks. But this example uses ftp://
+            # The spec says that only http: and https: scheme can be used
+            # for extended autolinks. But this example uses ftp:.
             628,
+            # While the spec says nothing of it, the cmark-gfm implementation
+            # removes a <strong> tag inside another strong tag (but not if there
+            # is another tag in between). For now we don’t implement this
+            # undocumented behavior.
+            398, 426, 434 .. 436, 473 .. 475, 477,
             ],
            json_file => "${FindBin::Bin}/data/github.tests.json",
            test_url => 'https://github.github.com/gfm/#example-%d',