diff --git a/sw/lib/ocaml/expr_syntax.ml b/sw/lib/ocaml/expr_syntax.ml
index 269f959b85..f600a9cb2d 100644
--- a/sw/lib/ocaml/expr_syntax.ml
+++ b/sw/lib/ocaml/expr_syntax.ml
@@ -55,7 +55,7 @@ let sprint = fun ?call_assoc expr ->
         sprintf "%s(%s)" op (eval e1)
     | CallOperator (_,_) -> failwith "Operator should be binary or unary"
     | Call (i, [Ident s]) when Some i = n ->
-        let index = try List.assoc s l with Not_found -> failwith (sprintf "Unknown block: '%s'" s) in
+        let index = try List.assoc s l with Not_found -> failwith (sprintf "Expr_syntax call_assoc not found: '%s'" s) in
         sprintf "%d" index
     | Call (i, es) ->
         let ses = List.map eval es in
diff --git a/sw/lib/ocaml/fp_proc.ml b/sw/lib/ocaml/fp_proc.ml
index be245bc784..1d7b7be09c 100644
--- a/sw/lib/ocaml/fp_proc.ml
+++ b/sw/lib/ocaml/fp_proc.ml
@@ -43,18 +43,19 @@ let parse_expression = fun s ->
           s (Lexing.lexeme_char lexbuf 0);
         exit 1
     | Parsing.Parse_error ->
-      fprintf stderr "Parsing error in '%s', token '%s' ?\n"
+      fprintf stderr "Fp_proc: Parsing error in '%s', token '%s' ?\n"
         s (Lexing.lexeme lexbuf);
       exit 1
 
 
 open Latlong
 
-let subst_expression = fun env e ->
+let subst_expression = fun (name, env) e ->
   let rec sub = fun e ->
     match e with
         Ident i -> Ident (try List.assoc i env with Not_found -> i)
       | Int _ | Float _ | Field _ -> e
+      | Call ("IndexOfBlock", [Ident s]) -> Call ("IndexOfBlock", [ Ident ("'"^name^"."^s^"'") ]) (* prefix block name *)
       | Call (i, es) -> Call (i, List.map sub es)
       | CallOperator (i, es) -> CallOperator (i, List.map sub es)
       | Index (i,e) -> Index (i,sub e)
@@ -230,8 +231,8 @@ let parse_include = fun dir flight_plan include_xml ->
     and sectors = get_children "sectors" proc
     and header = get_pc_data "header" proc in
 
-    let exceptions = List.map (transform_exception prefix reroutes env) exceptions
-    and blocks = List.map (transform_block prefix reroutes env) blocks in
+    let exceptions = List.map (transform_exception prefix reroutes (proc_name, env)) exceptions
+    and blocks = List.map (transform_block prefix reroutes (proc_name, env)) blocks in
 
     List.fold_right
       append_children