diff --git a/lib/cimport.ml b/lib/cimport.ml
index 058b77a..cb5d2f8 100644
--- a/lib/cimport.ml
+++ b/lib/cimport.ml
@@ -511,26 +511,50 @@ type imported = {
    [foo] whose signature has a struct in it, and a collision there is refused
    for the whole program rather than for the one binding. *)
 let of_dump ~env ~taken ~bound_syms (d : dump) : imported =
-  let decls = ref [] and hidden = ref [] and by_name = Hashtbl.create 512 in
+  let decls = ref [] and hidden = ref [] in
+  (* Collisions are found before anything is emitted, and they take *every*
+     name in the colliding group down with them.
+
+     Resolving one by taking the first and refusing the rest is the tempting
+     shape and the wrong one: which C function ends up owning the Flan name
+     would then depend on the order the header happens to declare them in, so
+     moving two lines in somebody else's header silently rebinds a name a Flan
+     program is already calling. There is no reading of [spin-2d] that is
+     obviously right when the header offers both [Spin2D] and [spin2d], so
+     neither gets it, and both say why. The author disambiguates with a
+     hand-written declare-c, which is what that form is for.
+
+     [bound_syms] is excluded first: a C function the package already binds by
+     hand is not competing for an imported name at all, so it cannot collide
+     with one. *)
+  let candidates =
+    List.filter (fun f -> not (List.mem f.csym bound_syms)) d.fns
+  in
+  let groups = Hashtbl.create 512 in
+  List.iter
+    (fun f ->
+       let k = kebab f.csym in
+       Hashtbl.replace groups k (f.csym :: Option.value ~default:[]
+                                             (Hashtbl.find_opt groups k)))
+    candidates;
   List.iter
     (fun f ->
        let flan = kebab f.csym in
        let skip why = hidden := (flan, why) :: !hidden in
-       if List.mem f.csym bound_syms then
-         (* Not hidden: the name the package wrote for it is there and works.
-            This is the escape hatch doing its job. *)
-         ()
-       else if Hashtbl.mem taken flan || Hashtbl.mem taken (flan ^ "-c") then
+       match List.rev (Hashtbl.find groups flan) with
+       | _ :: _ :: _ as all ->
+         skip
+           (Printf.sprintf
+              "%s all kebab to %s, and which one got the name would depend on \
+               the order the header declares them in — so none of them takes \
+               it. Bind the one you want with a hand-written declare-c"
+              (String.concat ", " all) flan)
+       | _ ->
+       if Hashtbl.mem taken flan || Hashtbl.mem taken (flan ^ "-c") then
          skip
            (Printf.sprintf
               "%s would be the imported name of %s, and the package declares \
                %s already" flan f.csym flan)
-       else if Hashtbl.mem by_name flan then
-         skip
-           (Printf.sprintf
-              "%s and %s both kebab to %s, so the header cannot be imported \
-               whole — one of them needs a hand-written declare-c"
-              (Hashtbl.find by_name flan) f.csym flan)
        else if f.cvariadic then
          skip
            (Printf.sprintf
@@ -555,7 +579,6 @@ let of_dump ~env ~taken ~bound_syms (d : dump) : imported =
          with
          | Error why -> skip (Printf.sprintf "%s %s" f.csym why)
          | Ok (params, ret) ->
-           Hashtbl.replace by_name flan f.csym;
            decls :=
              { Ast.d =
                  Ast.DeclareC
@@ -563,8 +586,18 @@ let of_dump ~env ~taken ~bound_syms (d : dump) : imported =
                     f.csym);
                dloc = f.cloc }
              :: !decls)
-    d.fns;
-  { decls = List.rev !decls; hidden = List.rev !hidden }
+    candidates;
+  (* One entry per name. A collision refuses every member of its group and each
+     of them writes the same reason under the same name, which [refuse_hidden]
+     would look up identically but a report would print twice. *)
+  let seen = Hashtbl.create 64 in
+  let hidden =
+    List.filter
+      (fun (n, _) ->
+         if Hashtbl.mem seen n then false else (Hashtbl.add seen n (); true))
+      (List.rev !hidden)
+  in
+  { decls = List.rev !decls; hidden }
 
 (* ── Checking the package's layouts against the header's ───────────── *)