diff --git a/scripts/startup/keyingsets_builtins.py b/scripts/startup/keyingsets_builtins.py
index fae3cd49563..99645fc2924 100644
--- a/scripts/startup/keyingsets_builtins.py
+++ b/scripts/startup/keyingsets_builtins.py
@@ -519,6 +519,9 @@ class WholeCharacterMixin:
                     # This happens when a custom property is set to None. In that case it cannot
                     # be converted to an FCurve-compatible value, so we can't keyframe it anyway.
                     continue
+                if not rna_property:
+                    # Failure to resolve property.
+                    continue
                 if rna_property.rna_type in prop_type_compat:
                     self.addProp(ks, bone, prop_path)
             elif prop_rna.is_animatable: