diff --git a/qualtran/bloqs/data_loading/qroam_clean.py b/qualtran/bloqs/data_loading/qroam_clean.py
index bb70cb98f..91f076796 100644
--- a/qualtran/bloqs/data_loading/qroam_clean.py
+++ b/qualtran/bloqs/data_loading/qroam_clean.py
@@ -155,8 +155,8 @@ def build_from_bitsize(
 
     @log_block_sizes.default
     def _default_log_block_sizes(self) -> Tuple[SymbolicInt, ...]:
-        target_bitsize = sum(self.target_bitsizes) * sum(
-            prod(shape) for shape in self.target_shapes
+        target_bitsize = sum(
+            bs * prod(shape) for (bs, shape) in zip(self.target_bitsizes, self.target_shapes)
         )
         return tuple(
             get_optimal_log_block_size_clean_ancilla(ilen, target_bitsize, adjoint=True)
@@ -256,8 +256,8 @@ def _target_reg_side(self) -> Side:
 
     @log_block_sizes.default
     def _default_log_block_sizes(self) -> Tuple[SymbolicInt, ...]:
-        target_bitsize = sum(self.target_bitsizes) * sum(
-            prod(shape) for shape in self.target_shapes
+        target_bitsize = sum(
+            bs * prod(shape) for (bs, shape) in zip(self.target_bitsizes, self.target_shapes)
         )
         return tuple(
             get_optimal_log_block_size_clean_ancilla(ilen, target_bitsize)
diff --git a/qualtran/bloqs/data_loading/qroam_clean_test.py b/qualtran/bloqs/data_loading/qroam_clean_test.py
index 932e9848c..7bc3b792f 100644
--- a/qualtran/bloqs/data_loading/qroam_clean_test.py
+++ b/qualtran/bloqs/data_loading/qroam_clean_test.py
@@ -18,6 +18,7 @@
 from qualtran.bloqs.data_loading.qroam_clean import (
     _qroam_clean_multi_data,
     _qroam_clean_multi_dim,
+    get_optimal_log_block_size_clean_ancilla,
     QROAMClean,
     QROAMCleanAdjoint,
 )
@@ -61,6 +62,19 @@ def test_t_complexity_2d_data_symbolic():
     assert bloq_inv.t_complexity().t == 4 * expected_toffoli_inv
 
 
+@pytest.mark.parametrize('n', range(3, 8))
+def test_qroam_default_log_block_sizes(n: int):
+    data = np.arange(2**n)
+    bloq = QROAMClean.build_from_data(data, data, target_bitsizes=(n.bit_length(), n.bit_length()))
+    bs = get_optimal_log_block_size_clean_ancilla(len(data), sum(bloq.target_bitsizes))
+    assert bs == bloq.log_block_sizes[0]
+    bloq = bloq.adjoint()
+    bs = get_optimal_log_block_size_clean_ancilla(
+        len(data), sum(bloq.target_bitsizes), adjoint=True
+    )
+    assert bs == bloq.log_block_sizes[0]
+
+
 def test_qroam_clean_classical_sim():
     rng = np.random.default_rng(42)
     # 1D data, 1 dataset