diff --git a/infer/src/bufferoverrun/absLoc.ml b/infer/src/bufferoverrun/absLoc.ml
index ff72ae746..2aca99e2e 100644
--- a/infer/src/bufferoverrun/absLoc.ml
+++ b/infer/src/bufferoverrun/absLoc.ml
@@ -12,20 +12,24 @@ open! IStd
 module F = Format
 
 module Allocsite = struct
-  include String
+  type t = Unknown | Known of {proc_name: string; node_hash: int; inst_num: int; dimension: int}
+  [@@deriving compare]
+
+  let pp fmt = function
+    | Unknown ->
+        F.fprintf fmt "Unknown"
+    | Known {proc_name : string; node_hash : int; inst_num : int; dimension : int} ->
+        F.fprintf fmt "%s-%d-%d-%d" proc_name node_hash inst_num dimension
 
-  let pp fmt s = Format.pp_print_string fmt s
+
+  let to_string x = F.asprintf "%a" pp x
 
   let make : Typ.Procname.t -> node_hash:int -> inst_num:int -> dimension:int -> t =
    fun proc_name ~node_hash ~inst_num ~dimension ->
-    let proc_name = Typ.Procname.to_string proc_name in
-    let node_num = string_of_int node_hash in
-    let inst_num = string_of_int inst_num in
-    let dimension = string_of_int dimension in
-    proc_name ^ "-" ^ node_num ^ "-" ^ inst_num ^ "-" ^ dimension
+    Known {proc_name= Typ.Procname.to_string proc_name; node_hash; inst_num; dimension}
 
 
-  let unknown = "Unknown"
+  let unknown = Unknown
 end
 
 module Loc = struct