diff --git a/mercurial/localrepo.py b/mercurial/localrepo.py
--- a/mercurial/localrepo.py
+++ b/mercurial/localrepo.py
@@ -438,6 +438,19 @@
     # Then we validate that the known set is reasonable to use together.
     ensurerequirementscompatible(ui, requirements)
 
+    # TODO there are unhandled edge cases related to opening repositories with
+    # shared storage. If storage is shared, we should also test for requirements
+    # compatibility in the pointed-to repo. This entails loading the .hg/hgrc in
+    # that repo, as that repo may load extensions needed to open it. This is a
+    # bit complicated because we don't want the other hgrc to overwrite settings
+    # in this hgrc.
+    #
+    # This bug is somewhat mitigated by the fact that we copy the .hg/requires
+    # file when sharing repos. But if a requirement is added after the share is
+    # performed, thereby introducing a new requirement for the opener, we may
+    # will not see that and could encounter a run-time error interacting with
+    # that shared store since it has an unknown-to-us requirement.
+
     # At this point, we know we should be capable of opening the repository.
     # Now get on with doing that.
 
diff --git a/tests/test-share.t b/tests/test-share.t
--- a/tests/test-share.t
+++ b/tests/test-share.t
@@ -439,6 +439,29 @@
 
   $ rm -r thatdir
 
+Demonstrate buggy behavior around requirements validation
+See comment in localrepo.py:makelocalrepository() for more.
+
+  $ hg init sharenewrequires
+  $ hg share sharenewrequires shareoldrequires
+  updating working directory
+  0 files updated, 0 files merged, 0 files removed, 0 files unresolved
+
+  $ cat >> sharenewrequires/.hg/requires << EOF
+  > missing-requirement
+  > EOF
+
+We cannot open the repo with the unknown requirement
+
+  $ hg -R sharenewrequires status
+  abort: repository requires features unknown to this Mercurial: missing-requirement!
+  (see https://mercurial-scm.org/wiki/MissingRequirement for more information)
+  [255]
+
+BUG: we don't get the same error when opening the shared repo pointing to it
+
+  $ hg -R shareoldrequires status
+
 Explicitly kill daemons to let the test exit on Windows
 
   $ killdaemons.py