diff --git a/src/pyobo/sources/famplex.py b/src/pyobo/sources/famplex.py
index 29011bf7..d0441815 100644
--- a/src/pyobo/sources/famplex.py
+++ b/src/pyobo/sources/famplex.py
@@ -151,9 +151,11 @@ def _get_xref_df(version: str) -> Mapping[str, List[Reference]]:
     }
     xrefs_df[0] = xrefs_df[0].map(lambda s: ns_remapping.get(s, s))
     xrefs_df[1] = [
-        bioregistry.standardize_identifier(xref_prefix, xref_identifier)
-        if xref_prefix != "nextprot.family"
-        else xref_identifier[len("FA:") :]
+        (
+            bioregistry.standardize_identifier(xref_prefix, xref_identifier)
+            if xref_prefix != "nextprot.family"
+            else xref_identifier[len("FA:") :]
+        )
         for xref_prefix, xref_identifier in xrefs_df[[0, 1]].values
     ]
 
diff --git a/src/pyobo/struct/struct.py b/src/pyobo/struct/struct.py
index c318848b..03c79f80 100644
--- a/src/pyobo/struct/struct.py
+++ b/src/pyobo/struct/struct.py
@@ -395,9 +395,7 @@ def _definition_fp(self) -> str:
 
     def iterate_relations(self) -> Iterable[Tuple[TypeDef, Reference]]:
         """Iterate over pairs of typedefs and targets."""
-        for typedef, targets in sorted(
-            self.relationships.items(), key=lambda pair: pair[0].preferred_curie
-        ):
+        for typedef, targets in sorted(self.relationships.items(), key=_sort_relations):
             for target in sorted(targets, key=lambda ref: ref.preferred_curie):
                 yield typedef, target
 
@@ -468,7 +466,7 @@ def _escape(s) -> str:
 
 def _sort_relations(r):
     typedef, _references = r
-    return typedef.reference.name or typedef.reference.identifier
+    return typedef.preferred_curie
 
 
 def _sort_properties(r):