diff --git a/src/passes/8-typer-new/heuristic_break_ctor.ml b/src/passes/8-typer-new/heuristic_break_ctor.ml
index e676f2500..1c0c63e60 100644
--- a/src/passes/8-typer-new/heuristic_break_ctor.ml
+++ b/src/passes/8-typer-new/heuristic_break_ctor.ml
@@ -3,7 +3,7 @@
 
 open Ast_typed.Misc
 open Ast_typed.Types
-open Solver_types
+open Typesystem.Solver_types
 
 let selector :  (type_constraint_simpl, output_break_ctor) selector =
   (* find two rules with the shape x = k(var …) and x = k'(var' …) *)
diff --git a/src/passes/8-typer-new/heuristic_specialize1.ml b/src/passes/8-typer-new/heuristic_specialize1.ml
index 6e481fc12..271f695f6 100644
--- a/src/passes/8-typer-new/heuristic_specialize1.ml
+++ b/src/passes/8-typer-new/heuristic_specialize1.ml
@@ -6,7 +6,7 @@
 module Core = Typesystem.Core
 open Ast_typed.Misc
 open Ast_typed.Types
-open Solver_types
+open Typesystem.Solver_types
 
 let selector : (type_constraint_simpl, output_specialize1) selector =
   (* find two rules with the shape (x = forall b, d) and x = k'(var' …) or vice versa *)
diff --git a/src/passes/8-typer-new/normalizer.ml b/src/passes/8-typer-new/normalizer.ml
index 8c391c2d5..5c6549c03 100644
--- a/src/passes/8-typer-new/normalizer.ml
+++ b/src/passes/8-typer-new/normalizer.ml
@@ -2,7 +2,7 @@ module Core = Typesystem.Core
 module Map = RedBlackTrees.PolyMap
 open Ast_typed.Misc
 open Ast_typed.Types
-open Solver_types
+open Typesystem.Solver_types
 
 (* sub-sub component: constraint normalizer: remove dupes and give structure
  * right now: union-find of unification vars
diff --git a/src/passes/8-typer-new/solver.ml b/src/passes/8-typer-new/solver.ml
index 0bcbe1260..c302befaf 100644
--- a/src/passes/8-typer-new/solver.ml
+++ b/src/passes/8-typer-new/solver.ml
@@ -4,7 +4,7 @@ module Map = RedBlackTrees.PolyMap
 module Set = RedBlackTrees.PolySet
 module UF = UnionFind.Poly2
 open Ast_typed.Types
-open Solver_types
+open Typesystem.Solver_types
 
 (* sub-sub component: lazy selector (don't re-try all selectors every time)
  * For now: just re-try everytime *)
diff --git a/src/passes/8-typer-new/solver_types.ml b/src/stages/typesystem/solver_types.ml
similarity index 100%
rename from src/passes/8-typer-new/solver_types.ml
rename to src/stages/typesystem/solver_types.ml
diff --git a/src/stages/typesystem/typesystem.ml b/src/stages/typesystem/typesystem.ml
index 75d8ee5b8..852d7543c 100644
--- a/src/stages/typesystem/typesystem.ml
+++ b/src/stages/typesystem/typesystem.ml
@@ -1,3 +1,4 @@
 module Core = Core
 module Shorthands = Shorthands
 module Misc = Misc
+module Solver_types = Solver_types