diff --git a/src/cc/Sidekick_cc.ml b/src/cc/Sidekick_cc.ml
index 9f48086b..dec46ea5 100644
--- a/src/cc/Sidekick_cc.ml
+++ b/src/cc/Sidekick_cc.ml
@@ -139,6 +139,17 @@ module Make(CC_A: ARG) = struct
 
   module N_tbl = CCHashtbl.Make(N)
 
+  (* non-recursive, inlinable function for [find] *)
+  let[@inline] find_ (n:node) : repr =
+    let n2 = n.n_root in
+    assert (N.is_root n2);
+    n2
+
+  let[@inline] same_class (n1:node)(n2:node): bool =
+    N.equal (find_ n1) (find_ n2)
+
+  let[@inline] find _ n = find_ n
+
   module Expl = struct
     type t = explanation
 
@@ -153,7 +164,9 @@ module Make(CC_A: ARG) = struct
 
     let mk_reduction : t = E_reduction
     let[@inline] mk_congruence n1 n2 : t = E_congruence (n1,n2)
-    let[@inline] mk_merge a b : t = if N.equal a b then mk_reduction else E_merge (a,b)
+    let[@inline] mk_merge a b : t = 
+      assert (same_class a b); 
+      if N.equal a b then mk_reduction else E_merge (a,b)
     let[@inline] mk_merge_t a b : t = if T.equal a b then mk_reduction else E_merge_t (a,b)
     let[@inline] mk_lit l : t = E_lit l
 
@@ -271,16 +284,6 @@ module Make(CC_A: ARG) = struct
      Invariant: [in_cc t ∧ do_cc t => forall u subterm t, in_cc u] *)
   let[@inline] mem (cc:t) (t:term): bool = T_tbl.mem cc.tbl t
 
-  (* non-recursive, inlinable function for [find] *)
-  let[@inline] find_ (n:node) : repr =
-    let n2 = n.n_root in
-    assert (N.is_root n2);
-    n2
-
-  let[@inline] same_class (n1:node)(n2:node): bool =
-    N.equal (find_ n1) (find_ n2)
-
-  let[@inline] find _ n = find_ n
 
   (* print full state *)
   let pp_full out (cc:t) : unit =