diff --git a/src/algorithms/toolbox.jl b/src/algorithms/toolbox.jl
index 4f548dada..86fcf64d7 100644
--- a/src/algorithms/toolbox.jl
+++ b/src/algorithms/toolbox.jl
@@ -56,7 +56,7 @@ Concretely, this is the overlap of the current state with the single-site deriva
 ```
 """
 function calc_galerkin(
-        pos::Int, below::Union{InfiniteMPS, FiniteMPS, WindowMPS}, operator, above, envs
+        pos, below::AbstractMPS, operator, above, envs
     )
     AC´ = AC_hamiltonian(pos, below, operator, above, envs) * above.AC[pos]
     normalize!(AC´)
@@ -71,7 +71,7 @@ function calc_galerkin(
     return calc_galerkin(col, below[row + 1], operator[row], above[row], envs[row])
 end
 function calc_galerkin(
-        below::Union{InfiniteMPS, FiniteMPS, WindowMPS}, operator, above, envs
+        below::AbstractMPS, operator, above, envs
     )
     return maximum(pos -> calc_galerkin(pos, below, operator, above, envs), 1:length(above))
 end