diff --git a/src/relay/pass/combine_parallel_conv2d.cc b/src/relay/pass/combine_parallel_conv2d.cc
index 3d9fb5891c2a9..60f643e436b2d 100644
--- a/src/relay/pass/combine_parallel_conv2d.cc
+++ b/src/relay/pass/combine_parallel_conv2d.cc
@@ -100,7 +100,7 @@ Expr MakeCombinedConv2D(const Expr& data, const std::vector<const CallNode*>& co
 Expr CombineParallelConv2D(const Expr& expr) {
   // data -> array of conv2d with the same input
   auto children_map = SiblingConv2DFinder().Find(expr);
-  Map<Expr, Expr> subst_map;
+  std::unordered_map<Expr, Expr, NodeHash, NodeEqual> subst_map;
 
   for (const auto& pair : children_map) {
     Expr data = pair.first;
@@ -150,7 +150,7 @@ Expr CombineParallelConv2D(const Expr& expr) {
         CHECK_NE(channel_index, std::string::npos);
         auto take = MakeTake(new_conv2d, indices, channel_index);
         start += *channels;
-        subst_map.Set(GetRef<Call>(conv2d), take);
+        subst_map[GetRef<Call>(conv2d)] = take;
       }
     }
   }
diff --git a/src/relay/pass/expr_subst.cc b/src/relay/pass/expr_subst.cc
index bac66bc0acf1c..586f748abef57 100644
--- a/src/relay/pass/expr_subst.cc
+++ b/src/relay/pass/expr_subst.cc
@@ -12,7 +12,8 @@ namespace relay {
 
 class ExprSubstituter : public ExprMutator {
  public:
-  explicit ExprSubstituter(tvm::Map<Expr, Expr> subst_map) : subst_map_(subst_map) {}
+  explicit ExprSubstituter(std::unordered_map<Expr, Expr, NodeHash, NodeEqual> subst_map)
+      : subst_map_(subst_map) {}
 
   Expr VisitExpr(const Expr& expr) final {
     auto it = subst_map_.find(expr);
@@ -26,7 +27,7 @@ class ExprSubstituter : public ExprMutator {
   tvm::Map<Expr, Expr> subst_map_;
 };
 
-Expr ExprSubst(const Expr& expr, tvm::Map<Expr, Expr> subst_map) {
+Expr ExprSubst(const Expr& expr, std::unordered_map<Expr, Expr, NodeHash, NodeEqual> subst_map) {
   return ExprSubstituter(std::move(subst_map)).Mutate(expr);
 }
 
diff --git a/src/relay/pass/expr_subst.h b/src/relay/pass/expr_subst.h
index 02f4179dae66e..67892b3a0af7d 100644
--- a/src/relay/pass/expr_subst.h
+++ b/src/relay/pass/expr_subst.h
@@ -6,11 +6,12 @@
 #ifndef TVM_RELAY_PASS_EXPR_SUBST_H_
 #define TVM_RELAY_PASS_EXPR_SUBST_H_
 #include <tvm/relay/expr.h>
+#include <unordered_map>
 
 namespace tvm {
 namespace relay {
 
-Expr ExprSubst(const Expr& expr, tvm::Map<Expr, Expr> subst_map);
+Expr ExprSubst(const Expr& expr, std::unordered_map<Expr, Expr, NodeHash, NodeEqual> subst_map);
 
 }  // namespace relay
 }  // namespace tvm