diff --git a/src/plugins/instantiate/Instantiate.mli b/src/plugins/instantiate/Instantiate.mli
index 061723344f1df682af0b1900e95324f0cc451b5e..d47de410b8fddfe50846106aa801e72f649dd4a8 100644
--- a/src/plugins/instantiate/Instantiate.mli
+++ b/src/plugins/instantiate/Instantiate.mli
@@ -41,19 +41,20 @@ module Instantiator_builder: sig
     (** Name of the implemented instantiator function *)
     val function_name: string
 
-    (** [well_typed_call ret args] must return true if and only if the
+    (** [well_typed_call ret fct args] must return true if and only if the
         corresponding call is well typed in the sens that the generator can
         produce a function override for the corresponding return value and
         parameters, according to their types and/or values.
     *)
-    val well_typed_call: lval option -> exp list -> bool
+    val well_typed_call: lval option -> varinfo -> exp list -> bool
 
-    (** [key_from_call ret args] must return an identifier for the corresponding
-        call. [key_from_call ret1 args1] and [key_from_call ret2 args2] must equal
-        if and only if the same override function can be used for both call. Any
-        call for which [well_typed_call] returns true must be able to give a key.
+    (** [key_from_call ret fct args] must return an identifier for the
+        corresponding call. [key_from_call ret1 fct1 args1] and
+        [key_from_call ret2 fct2 args2] must equal if and only if the same
+        override function can be used for both call. Any call for which
+        [well_typed_call] returns true must be able to give a key.
     *)
-    val key_from_call: lval option -> exp list -> override_key
+    val key_from_call: lval option -> varinfo -> exp list -> override_key
 
     (** [retype_args key args] must returns a new argument list compatible with
         the function identified by [override_key]. [args] is the list of arguments
diff --git a/src/plugins/instantiate/instantiator_builder.ml b/src/plugins/instantiate/instantiator_builder.ml
index 6b98b3ad9d26c521d5cbb90be41c7c45bed3383f..74242ed7bb5f1a50f2fbde264954abda3404141e 100644
--- a/src/plugins/instantiate/instantiator_builder.ml
+++ b/src/plugins/instantiate/instantiator_builder.ml
@@ -28,8 +28,8 @@ module type Generator_sig = sig
   type override_key = Hashtbl.key
 
   val function_name: string
-  val well_typed_call: lval option -> exp list -> bool
-  val key_from_call: lval option -> exp list -> override_key
+  val well_typed_call: lval option -> varinfo -> exp list -> bool
+  val key_from_call: lval option -> varinfo -> exp list -> override_key
   val retype_args: override_key -> exp list -> exp list
   val args_for_original: override_key -> exp list -> exp list
   val generate_prototype: override_key -> (string * typ)
@@ -41,8 +41,8 @@ module type Instantiator = sig
   type override_key
 
   val function_name: string
-  val well_typed_call: lval option -> exp list -> bool
-  val key_from_call: lval option -> exp list -> override_key
+  val well_typed_call: lval option -> varinfo -> exp list -> bool
+  val key_from_call: lval option -> varinfo -> exp list -> override_key
   val retype_args: override_key -> exp list -> exp list
   val get_override: override_key -> fundec
   val get_kfs: unit -> kernel_function list
diff --git a/src/plugins/instantiate/instantiator_builder.mli b/src/plugins/instantiate/instantiator_builder.mli
index 87c268d2d49824682e3f4e2d0ddfa18cd7d081ba..b0eb2f79fcf975b1957079beed9ac29d32c14e6d 100644
--- a/src/plugins/instantiate/instantiator_builder.mli
+++ b/src/plugins/instantiate/instantiator_builder.mli
@@ -40,19 +40,20 @@ module type Generator_sig = sig
   (** Name of the implemented function *)
   val function_name: string
 
-  (** [well_typed_call ret args] must return true if and only if the
+  (** [well_typed_call ret fct args] must return true if and only if the
       corresponding call is well typed in the sens that the generator can
       produce a function override for the corresponding return value and
       parameters, according to their types and/or values.
   *)
-  val well_typed_call: lval option -> exp list -> bool
+  val well_typed_call: lval option -> varinfo -> exp list -> bool
 
-  (** [key_from_call ret args] must return an identifier for the corresponding
-      call. [key_from_call ret1 args1] and [key_from_call ret2 args2] must equal
-      if and only if the same override function can be used for both call. Any
-      call for which [well_typed_call] returns true must be able to give a key.
+  (** [key_from_call ret fct args] must return an identifier for the
+      corresponding call. [key_from_call ret1 fct1 args1] and
+      [key_from_call ret2 fct2 args2] must equal if and only if the same
+      override function can be used for both call. Any call for which
+      [well_typed_call] returns true must be able to give a key.
   *)
-  val key_from_call: lval option -> exp list -> override_key
+  val key_from_call: lval option -> varinfo -> exp list -> override_key
 
   (** [retype_args key args] must returns a new argument list compatible with
       the function identified by [override_key]. [args] is the list of arguments
@@ -105,9 +106,9 @@ module type Instantiator = sig
   (** Same as [Generator_sig.override_key] *)
   val function_name: string
   (** Same as [Generator_sig.override_key] *)
-  val well_typed_call: lval option -> exp list -> bool
+  val well_typed_call: lval option -> varinfo -> exp list -> bool
   (** Same as [Generator_sig.override_key] *)
-  val key_from_call: lval option -> exp list -> override_key
+  val key_from_call: lval option -> varinfo -> exp list -> override_key
   (** Same as [Generator_sig.override_key] *)
   val retype_args: override_key -> exp list -> exp list
 
diff --git a/src/plugins/instantiate/stdlib/calloc.ml b/src/plugins/instantiate/stdlib/calloc.ml
index 1e064706c5b6eb1a4230eb414f71e60a1fc9689e..89af52fd24d8e1b71b7bc6468b506bdb65bf8c68 100644
--- a/src/plugins/instantiate/stdlib/calloc.ml
+++ b/src/plugins/instantiate/stdlib/calloc.ml
@@ -131,21 +131,21 @@ let generate_prototype alloc_type =
   ] in
   name, (TFun((ptr_of alloc_type), Some params, false, []))
 
-let well_typed_call ret args =
+let well_typed_call ret fct args =
   match ret, args with
-  | Some ret, [ _ ; _ ] ->
+  | Some ret, [ _ ; _ ] when Cil.hasAttribute "fc_stdlib" fct.vattr ->
     let t = Cil.typeOfLval ret in
     Cil.isPointerType t && not (Cil.isVoidPtrType t) &&
     Cil.isCompleteType (Cil.typeOf_pointed t)
   | _ -> false
 
-let key_from_call ret _ =
+let key_from_call ret fct _ =
   match ret with
-  | Some ret ->
+  | Some ret when Cil.hasAttribute "fc_stdlib" fct.vattr ->
     let ret_t = Cil.unrollTypeDeep (Cil.typeOfLval ret) in
     let ret_t = Cil.type_remove_qualifier_attributes_deep ret_t in
     Cil.typeOf_pointed ret_t
-  | None -> unexpected "trying to generate a key on an ill-typed call"
+  | _ -> unexpected "trying to generate a key on an ill-typed call"
 
 let retype_args _typ args = args
 let args_for_original _typ args = args
diff --git a/src/plugins/instantiate/stdlib/free.ml b/src/plugins/instantiate/stdlib/free.ml
index 7ef4c509bb20f13e505b79ab71a2feabc99d5436..ec63f84f4aa307d5cec0d97d4ba8f6c5b8f25d0b 100644
--- a/src/plugins/instantiate/stdlib/free.ml
+++ b/src/plugins/instantiate/stdlib/free.ml
@@ -83,16 +83,16 @@ let generate_prototype alloc_t =
   ] in
   name, (TFun(Cil.voidType, Some params, false, []))
 
-let well_typed_call _ret args =
+let well_typed_call _ret fct args =
   match args with
-  | [ ptr ] ->
+  | [ ptr ] when Cil.hasAttribute "fc_stdlib" fct.vattr ->
     let t = Cil.typeOf (Cil.stripCasts ptr) in
     Cil.isPointerType t && not (Cil.isVoidPtrType t)
   | _ -> false
 
-let key_from_call _ret args =
+let key_from_call _ret fct args =
   match args with
-  | [ ptr ] ->
+  | [ ptr ] when Cil.hasAttribute "fc_stdlib" fct.vattr ->
     let ptr = Cil.stripCasts ptr in
     let ptr_t = Cil.unrollTypeDeep (Cil.typeOf ptr) in
     let ptr_t = Cil.type_remove_qualifier_attributes_deep ptr_t in
diff --git a/src/plugins/instantiate/stdlib/malloc.ml b/src/plugins/instantiate/stdlib/malloc.ml
index 16521b530aebe5561a445c1e30216d24b338feef..fbf3374bcdd266c04f82936c4a422e903f64b196 100644
--- a/src/plugins/instantiate/stdlib/malloc.ml
+++ b/src/plugins/instantiate/stdlib/malloc.ml
@@ -70,21 +70,21 @@ let generate_prototype alloc_t =
   ] in
   name, (TFun((ptr_of alloc_t), Some params, false, []))
 
-let well_typed_call ret args =
+let well_typed_call ret fct args =
   match ret, args with
-  | Some ret, [ _ ] ->
+  | Some ret, [ _ ] when Cil.hasAttribute "fc_stdlib" fct.vattr ->
     let t = Cil.typeOfLval ret in
     Cil.isPointerType t && not (Cil.isVoidPtrType t) &&
     Cil.isCompleteType (Cil.typeOf_pointed t)
   | _ -> false
 
-let key_from_call ret _ =
+let key_from_call ret fct _ =
   match ret with
-  | Some ret ->
+  | Some ret when Cil.hasAttribute "fc_stdlib" fct.vattr ->
     let ret_t = Cil.unrollTypeDeep (Cil.typeOfLval ret) in
     let ret_t = Cil.type_remove_qualifier_attributes_deep ret_t in
     Cil.typeOf_pointed ret_t
-  | None -> unexpected "trying to generate a key on an ill-typed call"
+  | _ -> unexpected "trying to generate a key on an ill-typed call"
 
 let retype_args _typ args = args
 let args_for_original _typ args = args
diff --git a/src/plugins/instantiate/string/mem_utils.ml b/src/plugins/instantiate/string/mem_utils.ml
index 9d88bb79b94c2361688d64793874fc85360ca382..02ccd376309958c77e2e5701327a2567db8d2bbe 100644
--- a/src/plugins/instantiate/string/mem_utils.ml
+++ b/src/plugins/instantiate/string/mem_utils.ml
@@ -128,9 +128,10 @@ struct
     let name = F.name ^ "_" ^ (string_of_typ t) in
     name, ftype
 
-  let well_typed_call lval args =
+  let well_typed_call lval fct args =
     let _, ps = F.prototype () in
     if List.length args <> List.length ps then false
+    else if not (Cil.hasAttribute "fc_stdlib" fct.vattr) then false
     else
       let extract e = function
         | _, (CPtr | Ptr), _ -> exp_type_of_pointed e
@@ -157,10 +158,12 @@ struct
       in
       List.map2 retype args ps
 
-  let key_from_call _ret args =
+  let key_from_call _ret fct args =
     let _, ps = F.prototype () in
     match ps, args with
-    | (_, (Ptr|CPtr), _)::ps, fst::args when List.(length ps = length args) ->
+    | (_, (Ptr|CPtr), _) :: ps, fst :: args
+      when List.(length ps = length args)
+        && Cil.hasAttribute "fc_stdlib" fct.vattr ->
       begin match exp_type_of_pointed fst with
         | Value_of t -> t
         | _ ->
diff --git a/src/plugins/instantiate/string/mem_utils.mli b/src/plugins/instantiate/string/mem_utils.mli
index d4b205be01ee5ee4ca8cd05ec4b0630cd4e76202..fca57bd58d0ed47e5acccb5cb39bbe5fd55a12c8 100644
--- a/src/plugins/instantiate/string/mem_utils.mli
+++ b/src/plugins/instantiate/string/mem_utils.mli
@@ -44,9 +44,9 @@ end
 module Make (F: Function) : sig
   val generate_function_type : typ -> typ
   val generate_prototype : typ -> string * typ
-  val well_typed_call : lval option -> exp list -> bool
-  val retype_args : 'a -> exp list -> exp list
-  val key_from_call : 'a -> exp list -> typ
+  val well_typed_call : lval option -> varinfo -> exp list -> bool
+  val retype_args : typ -> exp list -> exp list
+  val key_from_call : lval option -> varinfo -> exp list ->  typ
 end
 
 (** location -> key -> s1 -> s2 -> len -> spec_result *)
diff --git a/src/plugins/instantiate/string/memset.ml b/src/plugins/instantiate/string/memset.ml
index b62c37aa2caf64cadded791992bd87d7c44eb2cc..21e44be2106cd71a710f2a9992cab90110011752 100644
--- a/src/plugins/instantiate/string/memset.ml
+++ b/src/plugins/instantiate/string/memset.ml
@@ -195,8 +195,8 @@ let rec contains_union_type t =
     contains_union_type t
   | _ -> false
 
-let well_typed_call _ret = function
-  | [ ptr ; value ; _ ] ->
+let well_typed_call _ret fct = function
+  | [ ptr ; value ; _ ] when Cil.hasAttribute "fc_stdlib" fct.vattr ->
     begin match Mem_utils.exp_type_of_pointed ptr, memset_value value with
       | (No_pointed | Of_null _) , _ -> false
       | Value_of t , _ when any_char_composed_type t -> true
@@ -208,8 +208,8 @@ let well_typed_call _ret = function
     end
   | _ -> false
 
-let key_from_call _ret = function
-  | [ ptr ; value ; _ ] ->
+let key_from_call _ret fct = function
+  | [ ptr ; value ; _ ] when Cil.hasAttribute "fc_stdlib" fct.vattr ->
     begin match Mem_utils.exp_type_of_pointed ptr, memset_value value with
       | Value_of t, _ when any_char_composed_type t -> t, None
       | Value_of t, value when not (contains_union_type t) -> t, value
diff --git a/src/plugins/instantiate/tests/api/external_instantiator_registration.ml b/src/plugins/instantiate/tests/api/external_instantiator_registration.ml
index b800bd1efbdd4bd92fe985fab4771f1f001c95cd..aa3c9b5c6a425206aeae937f7d69d88e2f9db39c 100644
--- a/src/plugins/instantiate/tests/api/external_instantiator_registration.ml
+++ b/src/plugins/instantiate/tests/api/external_instantiator_registration.ml
@@ -1,12 +1,12 @@
 let function_name = "mine"
 
-let well_typed_call _ = function
+let well_typed_call _ _ = function
   | [ e ] ->
     let t = Cil.typeOf(Cil.stripCasts e) in
     not (Cil.isVoidPtrType t) && Cil.isPointerType t
   | _ -> false
 
-let key_from_call _ = function
+let key_from_call _ _ = function
   | [ e ] ->
     let t = Cil.typeOf(Cil.stripCasts e) in
     Cil.typeOf_pointed t
diff --git a/src/plugins/instantiate/transform.ml b/src/plugins/instantiate/transform.ml
index c1f0f29d170495ca9c3421cf725d8c3d5c7a8d37..4970a5913e2b477160548a6b11b34155ad5124d2 100644
--- a/src/plugins/instantiate/transform.ml
+++ b/src/plugins/instantiate/transform.ml
@@ -90,8 +90,8 @@ class transformer = object(self)
   method private replace_call (lval, fct, args) =
     try
       let module I = (val (self#find_enabled_instantiator fct): Instantiator) in
-      if I.well_typed_call lval args then
-        let key = I.key_from_call lval args in
+      if I.well_typed_call lval fct args then
+        let key = I.key_from_call lval fct args in
         let fundec = I.get_override key in
         let new_args = I.retype_args key args in
         Queue.add fundec used_instantiator_last_kf ;