diff --git a/infer/src/nullsafe/models.ml b/infer/src/nullsafe/models.ml
index 94dab3f9c..740030b61 100644
--- a/infer/src/nullsafe/models.ml
+++ b/infer/src/nullsafe/models.ml
@@ -64,9 +64,7 @@ let is_check_not_null proc_name =
 (** Parameter number for a procedure known to be a checkNotNull *)
 let get_check_not_null_parameter proc_name =
   let proc_id = Typ.Procname.to_unique_id proc_name in
-  try Hashtbl.find check_not_null_parameter_table proc_id with Caml.Not_found ->
-    (* Assume the check is on the first parameter unless modeled otherwise *)
-    1
+  Hashtbl.find_opt check_not_null_parameter_table proc_id
 
 
 (** Check if the procedure is one of the known Preconditions.checkState. *)
diff --git a/infer/src/nullsafe/typeCheck.ml b/infer/src/nullsafe/typeCheck.ml
index e683de067..f325d534c 100644
--- a/infer/src/nullsafe/typeCheck.ml
+++ b/infer/src/nullsafe/typeCheck.ml
@@ -800,13 +800,15 @@ let typecheck_instr tenv calls_this checks (node : Procdesc.Node.t) idenv curr_p
               EradicateChecks.check_call_parameters tenv find_canonical_duplicate curr_pdesc node
                 callee_attributes resolved_params loc instr_ref ;
             if Models.is_check_not_null callee_pname then
-              if Typ.Procname.Java.is_vararg callee_pname_java then
-                let last_parameter = List.length call_params in
-                do_preconditions_check_not_null last_parameter ~is_vararg:true typestate1
-              else
-                do_preconditions_check_not_null
-                  (Models.get_check_not_null_parameter callee_pname)
-                  ~is_vararg:false typestate1
+              match Models.get_check_not_null_parameter callee_pname with
+              | Some index ->
+                  do_preconditions_check_not_null index ~is_vararg:false typestate1
+              | None when Typ.Procname.Java.is_vararg callee_pname_java ->
+                  let last_parameter = List.length call_params in
+                  do_preconditions_check_not_null last_parameter ~is_vararg:true typestate1
+              | None ->
+                  (* assume the first parameter is checked for null *)
+                  do_preconditions_check_not_null 1 ~is_vararg:false typestate1
             else if Models.is_check_state callee_pname || Models.is_check_argument callee_pname
             then do_preconditions_check_state typestate1
             else if Models.is_mapPut callee_pname then do_map_put typestate1