diff --git a/src/core/internal.ml b/src/core/internal.ml
index ca4a7e39..d97ab73e 100644
--- a/src/core/internal.ml
+++ b/src/core/internal.ml
@@ -287,7 +287,7 @@ module Make
       if a.neg.is_true then begin
         (* If a variable is false, we need to see why it is false. *)
         match a.var.reason with
-        | None | Some Decision | Some Assumption -> assert false
+        | None | Some Decision -> assert false
         (* The var must have a reason, and it cannot be a decision/assumption, since we are
            at level 0. *)
         | Some (Bcp cl) -> atoms, cl :: history
@@ -620,7 +620,7 @@ module Make
                     c := res
                   | _ -> assert false
                 end
-              | None | Some Decision | Some Assumption | Some Semantic _ -> ()
+              | None | Some Decision | Some Semantic _ -> ()
             end
       done; assert false
     with Exit ->
@@ -1110,7 +1110,8 @@ module Make
            let level = decision_level() in
            assert (env.base_level = level-1);
            env.base_level <- level;
-           enqueue_bool a ~level Assumption;
+           let c = make_clause (fresh_hname ()) [a] Hyp in
+           enqueue_bool a ~level (Bcp c);
            match propagate () with
              | Some confl -> (* Conflict *)
                report_unsat confl;
diff --git a/src/core/res.ml b/src/core/res.ml
index a4134879..d6df0526 100644
--- a/src/core/res.ml
+++ b/src/core/res.ml
@@ -136,7 +136,7 @@ module Make(St : Solver_types.S) = struct
     match conclusion.St.cpremise with
     | St.Lemma l ->
       {conclusion; step = Lemma l; }
-    | St.Hyp _ ->
+    | St.Hyp ->
       { conclusion; step = Hypothesis; }
     | St.History [] ->
       assert false
@@ -163,7 +163,7 @@ module Make(St : Solver_types.S) = struct
         if not c.St.visited then begin
           c.St.visited <- true;
           match c.St.cpremise with
-            | St.Hyp _ | St.Lemma _ -> aux (c :: res) acc r
+            | St.Hyp | St.Lemma _ -> aux (c :: res) acc r
             | St.History h ->
               let l = List.fold_left (fun acc c ->
                   if not c.St.visited then c :: acc else acc) r h in
diff --git a/src/core/solver_types.ml b/src/core/solver_types.ml
index 50adf37a..642d4724 100644
--- a/src/core/solver_types.ml
+++ b/src/core/solver_types.ml
@@ -68,7 +68,6 @@ module McMake (E : Expr_intf.S)(Dummy : sig end) = struct
     | Decision
     | Bcp of clause
     | Semantic of int
-    | Assumption
 
   and premise =
     | Hyp
@@ -267,7 +266,6 @@ module McMake (E : Expr_intf.S)(Dummy : sig end) = struct
     | n, Some Decision   -> sprintf "@@%d" n
     | n, Some Bcp c -> sprintf "->%d/%s" n c.name
     | n, Some Semantic lvl -> sprintf "::%d/%d" n lvl
-    | n, Some Assumption -> sprintf "!%d" n
 
   let value a =
     if a.is_true then sprintf "[T%s]" (level a)
diff --git a/src/core/solver_types_intf.ml b/src/core/solver_types_intf.ml
index 72556c0a..cad58fd9 100644
--- a/src/core/solver_types_intf.ml
+++ b/src/core/solver_types_intf.ml
@@ -63,7 +63,6 @@ module type S = sig
     | Decision
     | Bcp of clause
     | Semantic of int
-    | Assumption
 
   and premise =
     | Hyp