diff --git a/infer/src/IR/Procdesc.ml b/infer/src/IR/Procdesc.ml
index 6a64e3590..edb862819 100644
--- a/infer/src/IR/Procdesc.ml
+++ b/infer/src/IR/Procdesc.ml
@@ -297,13 +297,13 @@ let iter_instrs f pdesc =
   iter_nodes do_node pdesc
 
 
-let fold_nodes f acc pdesc = List.fold ~f ~init:acc (List.rev (get_nodes pdesc))
+let fold_nodes pdesc ~init ~f = List.fold ~f ~init (List.rev (get_nodes pdesc))
 
-let fold_instrs f acc pdesc =
+let fold_instrs pdesc ~init ~f =
   let fold_node acc node =
     List.fold ~f:(fun acc instr -> f acc node instr) ~init:acc (Node.get_instrs node)
   in
-  fold_nodes fold_node acc pdesc
+  fold_nodes ~f:fold_node ~init pdesc
 
 
 (** iterate between two nodes or until we reach a branching structure *)
diff --git a/infer/src/IR/Procdesc.mli b/infer/src/IR/Procdesc.mli
index 022abb88c..6352bb510 100644
--- a/infer/src/IR/Procdesc.mli
+++ b/infer/src/IR/Procdesc.mli
@@ -136,10 +136,10 @@ val create_node : t -> Location.t -> Node.nodekind -> Sil.instr list -> Node.t
 val did_preanalysis : t -> bool
 (** true if we ran the preanalysis on the CFG associated with [t] *)
 
-val fold_instrs : ('a -> Node.t -> Sil.instr -> 'a) -> 'a -> t -> 'a
+val fold_instrs : t -> init:'accum -> f:('accum -> Node.t -> Sil.instr -> 'accum) -> 'accum
 (** fold over all nodes and their instructions *)
 
-val fold_nodes : ('a -> Node.t -> 'a) -> 'a -> t -> 'a
+val fold_nodes : t -> init:'accum -> f:('accum -> Node.t -> 'accum) -> 'accum
 (** fold over all nodes *)
 
 val from_proc_attributes : ProcAttributes.t -> t
diff --git a/infer/src/absint/PatternMatch.ml b/infer/src/absint/PatternMatch.ml
index 5cbf7adda..402f7ae01 100644
--- a/infer/src/absint/PatternMatch.ml
+++ b/infer/src/absint/PatternMatch.ml
@@ -326,7 +326,8 @@ let get_fields_nullified procdesc =
         (nullified_flds, this_ids)
   in
   let nullified_flds, _ =
-    Procdesc.fold_instrs collect_nullified_flds (Typ.Fieldname.Set.empty, Ident.Set.empty) procdesc
+    Procdesc.fold_instrs procdesc ~f:collect_nullified_flds
+      ~init:(Typ.Fieldname.Set.empty, Ident.Set.empty)
   in
   nullified_flds
 
diff --git a/infer/src/bufferoverrun/bufferOverrunChecker.ml b/infer/src/bufferoverrun/bufferOverrunChecker.ml
index aaaa35412..09e2d099f 100644
--- a/infer/src/bufferoverrun/bufferOverrunChecker.ml
+++ b/infer/src/bufferoverrun/bufferOverrunChecker.ml
@@ -487,7 +487,7 @@ module Report = struct
   let collect : Specs.summary -> extras ProcData.t -> Analyzer.invariant_map -> PO.ConditionSet.t =
    fun summary ({pdesc} as pdata) inv_map ->
     let add_node1 acc node = collect_node summary pdata inv_map acc node in
-    Procdesc.fold_nodes add_node1 PO.ConditionSet.empty pdesc
+    Procdesc.fold_nodes pdesc ~f:add_node1 ~init:PO.ConditionSet.empty
 
 
   let make_err_trace : Trace.t -> string -> Errlog.loc_trace =
diff --git a/infer/src/checkers/BoundedCallTree.ml b/infer/src/checkers/BoundedCallTree.ml
index 70748fa57..74d8df659 100644
--- a/infer/src/checkers/BoundedCallTree.ml
+++ b/infer/src/checkers/BoundedCallTree.ml
@@ -36,11 +36,9 @@ let line_range_of_pdesc pdesc =
   let ploc = Procdesc.get_loc pdesc in
   let start_line = ploc.Location.line in
   let end_line =
-    Procdesc.fold_instrs
-      (fun acc _ instr ->
+    Procdesc.fold_instrs pdesc ~init:start_line ~f:(fun acc _ instr ->
         let new_loc = Sil.instr_get_loc instr in
         max acc new_loc.Location.line )
-      start_line pdesc
   in
   {Stacktree_j.start_line; end_line}