diff --git a/singer_sdk/helpers/_flattening.py b/singer_sdk/helpers/_flattening.py
index d5bc4afff..2a3e194d0 100644
--- a/singer_sdk/helpers/_flattening.py
+++ b/singer_sdk/helpers/_flattening.py
@@ -415,8 +415,12 @@ def _flatten_record(
     items: list[tuple[str, t.Any]] = []
     for k, v in record_node.items():
         new_key = flatten_key(k, parent_key, separator)
-        if isinstance(v, collections.abc.MutableMapping) and (
-            (flattened_schema and new_key not in flattened_schema.get("properties", {}))
+        # If the value is a dictionary, and the key is not in the schema, and the
+        # level is less than the max level, then we should continue to flatten.
+        if (
+            isinstance(v, collections.abc.MutableMapping)
+            and flattened_schema
+            and new_key not in flattened_schema.get("properties", {})
             and (level < max_level)
         ):
             items.extend(