diff --git a/engine-proto/Engine.Algebraic.jl b/engine-proto/Engine.Algebraic.jl
index b6fc7a7..f14f58c 100644
--- a/engine-proto/Engine.Algebraic.jl
+++ b/engine-proto/Engine.Algebraic.jl
@@ -120,11 +120,11 @@ equation(rel::AlignsWithBy) = mprod(rel.elements[1].vec, rel.elements[2].vec) -
 # --- constructions ---
 
 mutable struct Construction{T}
-  points::Set{Point{T}}
-  spheres::Set{Sphere{T}}
-  relations::Set{Relation{T}}
+  points::Vector{Point{T}}
+  spheres::Vector{Sphere{T}}
+  relations::Vector{Relation{T}}
   
-  function Construction{T}(; elements = Set{Element{T}}(), relations = Set{Relation{T}}()) where T
+  function Construction{T}(; elements = Vector{Element{T}}(), relations = Vector{Relation{T}}()) where T
     allelements = union(elements, (rel.elements for rel in relations)...)
     new{T}(
       filter(elt -> isa(elt, Point), allelements),
diff --git a/engine-proto/Engine.jl b/engine-proto/Engine.jl
index 0410f6d..d283e72 100644
--- a/engine-proto/Engine.jl
+++ b/engine-proto/Engine.jl
@@ -56,7 +56,7 @@ tangencies = [
   ##Engine.LiesOn{CoeffType}(points[3], spheres[1]),
   ##Engine.LiesOn{CoeffType}(points[3], spheres[2])
 ##]
-ctx_tan_sph = Engine.Construction{CoeffType}(elements = Set(spheres), relations = Set(tangencies))
+ctx_tan_sph = Engine.Construction{CoeffType}(elements = spheres, relations = tangencies)
 ideal_tan_sph, eqns_tan_sph = Engine.realize(ctx_tan_sph)
 ##small_eqns_tan_sph = eqns_tan_sph
 small_eqns_tan_sph = [