diff --git a/fix_1529.py b/fix_1529.py
new file mode 100644
index 000000000..34889ac82
--- /dev/null
+++ b/fix_1529.py
@@ -0,0 +1,43 @@
+# 1. Extract allowed fields to a constant
+ALLOWED_UPDATE_FIELDS = ['field1', 'field2', 'field3']
+
+class MemoryRecord:
+    def __init__(self, id, status, ownership, provenance, source_references):
+        self.id = id
+        self.status = status
+        self.ownership = ownership
+        self.provenance = provenance
+        self.source_references = source_references
+        self.field1 = None
+        self.field2 = None
+        self.field3 = None
+
+    def update(self, updates):
+        # 2. Validate all keys FIRST to ensure atomic updates
+        invalid_keys = [k for k in updates if k not in ALLOWED_UPDATE_FIELDS]
+        if invalid_keys:
+            raise ValueError(f"Unknown update field(s): {', '.join(invalid_keys)}")
+        
+        # 3. Apply updates only if all keys are valid
+        for key, value in updates.items():
+            setattr(self, key, value)
+
+class MemoryRecordRepository:
+    def __init__(self):
+        self.records = {}
+    def add_record(self, record):
+        self.records[record.id] = record
+    def update_record(self, id, updates):
+        if id not in self.records:
+            raise ValueError("Record does not exist")
+        self.records[id].update(updates)
+
+# 4. Pass repository as an argument and propagate exceptions
+def update_memory(id, updates, repository):
+    repository.update_record(id, updates)
+
+if __name__ == "__main__":
+    # Example usage
+    repo = MemoryRecordRepository()
+    repo.add_record(MemoryRecord('record_id', 'status', 'ownership', 'provenance', 'source_references'))
+    update_memory('record_id', {'field1': 'new_value', 'field4': 'new_value'}, repo)