diff --git a/arraycontext/impl/pytato/batched_einsum/utils.py b/arraycontext/impl/pytato/batched_einsum/utils.py
index 1a69299f..a8ff97d5 100644
--- a/arraycontext/impl/pytato/batched_einsum/utils.py
+++ b/arraycontext/impl/pytato/batched_einsum/utils.py
@@ -191,10 +191,14 @@ def apply_kennedy_fusion_with_batched_einsum_extension(
 
             if insn.reduction_inames():
                 einsum, _ = fnsm.get_a_matched_einsum(
-                    t_unit, insn_match=lp_match.Id(insn.id))
+                    t_unit, insn_match=lp_match.Id(insn.id),
+                    # only consider inames with same length for fusion
+                    # => do not parametrize inames with very long loop-counts.
+                    long_dim_length=np.inf)
                 einsum = fnsm.canonicalize_einsum(einsum)
                 subst_map = fnsm.match_t_unit_to_einsum(
-                    t_unit, einsum, insn_match=lp_match.Id(insn.id))
+                    t_unit, einsum, insn_match=lp_match.Id(insn.id),
+                    long_dim_length=np.inf)
             else:
                 # we treat any non-reduction einsum as a copy-einsum
                 assignee = insn.assignee