diff --git a/src/pyobo/struct/struct.py b/src/pyobo/struct/struct.py
index 54dbbe4d..c2769442 100644
--- a/src/pyobo/struct/struct.py
+++ b/src/pyobo/struct/struct.py
@@ -86,6 +86,9 @@
 SynonymSpecificity = Literal["EXACT", "NARROW", "BROAD", "RELATED"]
 SynonymSpecificities: Sequence[SynonymSpecificity] = ("EXACT", "NARROW", "BROAD", "RELATED")
 
+TermStanzaType: TypeAlias = Literal["Term", "Instance"]
+TERM_STANZA_SORT_PRIORITY: dict[TermStanzaType, int] = {"Instance": 2, "Term": 1}
+
 #: Columns in the SSSOM dataframe
 SSSOM_DF_COLUMNS = [
     "subject_id",
@@ -298,7 +301,7 @@ class Term(Referenced):
     #: An annotation for obsolescence. By default, is None, but this means that it is not obsolete.
     is_obsolete: bool | None = None
 
-    type: Literal["Term", "Instance"] = "Term"
+    type: TermStanzaType = "Term"
 
     def __hash__(self) -> int:
         # have to re-define hash because of the @dataclass
@@ -1335,8 +1338,20 @@ def write_default(
     @property
     def _items_accessor(self):
         if self._items is None:
+            if self.term_sort_key is not None:
+
+                def _sort_key(term: Term):
+                    # it appears that mypy has a bug and isn't able to pull
+                    # the outer if statement's constraint into the definition,
+                    # that's why there's a type ignore
+                    return TERM_STANZA_SORT_PRIORITY[term.type], self.term_sort_key(self, term)  # type:ignore
+            else:
+
+                def _sort_key(term: Term):
+                    return TERM_STANZA_SORT_PRIORITY[term.type], term.preferred_curie
+
             # if the term sort key is None, then the terms get sorted by their reference
-            self._items = sorted(self.iter_terms(force=self.force), key=self.term_sort_key)
+            self._items = sorted(self.iter_terms(force=self.force), key=_sort_key)
         return self._items
 
     def __iter__(self) -> Iterator[Term]: