diff --git a/ibis/backends/base/__init__.py b/ibis/backends/base/__init__.py
index 2041a54b73a5..d0aed452420b 100644
--- a/ibis/backends/base/__init__.py
+++ b/ibis/backends/base/__init__.py
@@ -1186,9 +1186,9 @@ def _cached(self, expr: ir.Table):
         if (result := self._query_cache.get(op)) is None:
             self._query_cache.store(expr)
             result = self._query_cache[op]
-        return ir.CachedTable(result)
+        return ir.CachedTableExpr(result)
 
-    def _release_cached(self, expr: ir.CachedTable) -> None:
+    def _release_cached(self, expr: ir.CachedTableExpr) -> None:
         """Releases the provided cached expression.
 
         Parameters
diff --git a/ibis/backends/duckdb/__init__.py b/ibis/backends/duckdb/__init__.py
index 972bda05a425..6bd93fa818a4 100644
--- a/ibis/backends/duckdb/__init__.py
+++ b/ibis/backends/duckdb/__init__.py
@@ -1467,7 +1467,7 @@ def _register_in_memory_table(self, op: ops.InMemoryTable) -> None:
                 # 2. broken for string[pyarrow] dtypes (segfault)
                 if conversions := {
                     colname: "str"
-                    for colname, col in table.items()
+                    for colname, col in getattr(table, "obj", table).items()
                     if isinstance(col.dtype, pd.StringDtype)
                 }:
                     table = table.astype(conversions)
@@ -1477,7 +1477,7 @@ def _register_in_memory_table(self, op: ops.InMemoryTable) -> None:
             # register creates a transaction, and we can't nest transactions so
             # we create a function to encapsulate the whole shebang
             def _register(name, table):
-                self.con.register(name, table)
+                self.con.register(name, getattr(table, "obj", table))
 
             try:
                 _register(name, table)