diff --git a/compiler/rustc_middle/src/mir/query.rs b/compiler/rustc_middle/src/mir/query.rs
index 0edb79fdbc8..f6c8ed4cbab 100644
--- a/compiler/rustc_middle/src/mir/query.rs
+++ b/compiler/rustc_middle/src/mir/query.rs
@@ -2,8 +2,8 @@
 
 use crate::mir::{abstract_const, Body, Promoted};
 use crate::ty::{self, Ty, TyCtxt};
-use rustc_data_structures::fx::FxHashMap;
 use rustc_data_structures::sync::Lrc;
+use rustc_data_structures::vec_map::VecMap;
 use rustc_errors::ErrorReported;
 use rustc_hir as hir;
 use rustc_hir::def_id::{DefId, LocalDefId};
@@ -210,7 +210,7 @@ pub struct BorrowCheckResult<'tcx> {
     /// All the opaque types that are restricted to concrete types
     /// by this function. Unlike the value in `TypeckResults`, this has
     /// unerased regions.
-    pub concrete_opaque_types: FxHashMap<DefId, ty::ResolvedOpaqueTy<'tcx>>,
+    pub concrete_opaque_types: VecMap<DefId, ty::ResolvedOpaqueTy<'tcx>>,
     pub closure_requirements: Option<ClosureRegionRequirements<'tcx>>,
     pub used_mut_upvars: SmallVec<[Field; 8]>,
 }
diff --git a/compiler/rustc_middle/src/ty/context.rs b/compiler/rustc_middle/src/ty/context.rs
index 970e669c16f..ee8fa4b647a 100644
--- a/compiler/rustc_middle/src/ty/context.rs
+++ b/compiler/rustc_middle/src/ty/context.rs
@@ -34,6 +34,7 @@
 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
 use rustc_data_structures::steal::Steal;
 use rustc_data_structures::sync::{self, Lock, Lrc, WorkerLocal};
+use rustc_data_structures::vec_map::VecMap;
 use rustc_errors::ErrorReported;
 use rustc_hir as hir;
 use rustc_hir::def::{DefKind, Res};
@@ -424,7 +425,7 @@ pub struct TypeckResults<'tcx> {
 
     /// All the opaque types that are restricted to concrete types
     /// by this function.
-    pub concrete_opaque_types: FxHashMap<DefId, ResolvedOpaqueTy<'tcx>>,
+    pub concrete_opaque_types: VecMap<DefId, ResolvedOpaqueTy<'tcx>>,
 
     /// Tracks the minimum captures required for a closure;
     /// see `MinCaptureInformationMap` for more details.
diff --git a/compiler/rustc_mir/src/borrow_check/mod.rs b/compiler/rustc_mir/src/borrow_check/mod.rs
index 36eb8a4baa8..5b2aaf56921 100644
--- a/compiler/rustc_mir/src/borrow_check/mod.rs
+++ b/compiler/rustc_mir/src/borrow_check/mod.rs
@@ -2,6 +2,7 @@
 
 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
 use rustc_data_structures::graph::dominators::Dominators;
+use rustc_data_structures::vec_map::VecMap;
 use rustc_errors::{Applicability, Diagnostic, DiagnosticBuilder, ErrorReported};
 use rustc_hir as hir;
 use rustc_hir::def_id::LocalDefId;
@@ -25,7 +26,7 @@
 use smallvec::SmallVec;
 use std::cell::RefCell;
 use std::collections::BTreeMap;
-use std::iter;
+use std::iter::{self, FromIterator};
 use std::mem;
 use std::rc::Rc;
 
@@ -441,7 +442,7 @@ fn do_mir_borrowck<'a, 'tcx>(
     }
 
     let result = BorrowCheckResult {
-        concrete_opaque_types: opaque_type_values,
+        concrete_opaque_types: VecMap::from_iter(opaque_type_values.into_iter()),
         closure_requirements: opt_closure_req,
         used_mut_upvars: mbcx.used_mut_upvars,
     };