diff --git a/src/arithmetic.jl b/src/arithmetic.jl
index 346a1a4..c25b898 100644
--- a/src/arithmetic.jl
+++ b/src/arithmetic.jl
@@ -140,23 +140,24 @@ function MA.operate_to!(
     ::typeof(*),
     args::Vararg{AlgebraElement,N},
 ) where {N}
-    for arg in args
-        @assert parent(res) == parent(arg)
-    end
-    mstr = mstructure(basis(res))
+    mstr = mstructure(parent(res), parent.(args)...)
     MA.operate_to!(coeffs(res), mstr, coeffs.(args)...)
     return res
 end
 
+function mstructure(args::AbstractStarAlgebra...)
+    for arg in args
+        @assert arg == first(args)
+    end
+    return mstructure(basis(args[1]))
+end
+
 function MA.operate!(
     ::UnsafeAddMul{typeof(*)},
     res::AlgebraElement,
     args::Vararg{AlgebraElement,N},
 ) where {N}
-    for arg in args
-        @assert parent(res) == parent(arg)
-    end
-    mstr = mstructure(basis(res))
+    mstr = mstructure(parent(res), parent.(args)...)
     MA.operate!(UnsafeAddMul(mstr), coeffs(res), coeffs.(args)...)
     return res
 end