diff --git a/src/abstractindsnetwork.jl b/src/abstractindsnetwork.jl
index d25f5abb..eda958f6 100644
--- a/src/abstractindsnetwork.jl
+++ b/src/abstractindsnetwork.jl
@@ -138,9 +138,13 @@ function insert_linkinds(
   for e in edges
     # TODO: Change to check if it is empty.
     if !isassigned(indsnetwork, e)
-      iₑ = Index(link_space, edge_tag(e))
-      # TODO: Allow setting with just `Index`.
-      indsnetwork[e] = [iₑ]
+      if !isnothing(link_space)
+        iₑ = Index(link_space, edge_tag(e))
+        # TODO: Allow setting with just `Index`.
+        indsnetwork[e] = [iₑ]
+      else
+        indsnetwork[e] = []
+      end
     end
   end
   return indsnetwork
diff --git a/src/formnetworks/bilinearformnetwork.jl b/src/formnetworks/bilinearformnetwork.jl
index 306cb4a1..19ca7568 100644
--- a/src/formnetworks/bilinearformnetwork.jl
+++ b/src/formnetworks/bilinearformnetwork.jl
@@ -65,7 +65,7 @@ function BilinearFormNetwork(
   @assert issetequal(flatten_siteinds(bra), flatten_siteinds(ket))
   operator_inds = union_all_inds(siteinds(ket), dual_site_index_map(siteinds(ket)))
   # TODO: Define and use `identity_network` here.
-  O = ITensorNetwork(Op("I"), operator_inds)
+  O = ITensorNetwork(Op("I"), operator_inds; link_space=nothing)
   return BilinearFormNetwork(O, bra, ket; dual_site_index_map, kwargs...)
 end