diff --git a/clang/include/clang/Serialization/ASTReader.h b/clang/include/clang/Serialization/ASTReader.h
index 1360ee1877c1a..af01bacbfdc42 100644
--- a/clang/include/clang/Serialization/ASTReader.h
+++ b/clang/include/clang/Serialization/ASTReader.h
@@ -988,6 +988,9 @@ class ASTReader
   ///Whether we are currently processing update records.
   bool ProcessingUpdateRecords = false;
 
+  /// Whether we are going to write modules.
+  bool FinalizedForWriting = false;
+
   using SwitchCaseMapTy = llvm::DenseMap<unsigned, SwitchCase *>;
 
   /// Mapping from switch-case IDs in the chain to switch-case statements
diff --git a/clang/lib/Serialization/ASTReader.cpp b/clang/lib/Serialization/ASTReader.cpp
index bdf476cf128a3..93409df3d4fc4 100644
--- a/clang/lib/Serialization/ASTReader.cpp
+++ b/clang/lib/Serialization/ASTReader.cpp
@@ -5089,7 +5089,8 @@ void ASTReader::InitializeContext() {
 }
 
 void ASTReader::finalizeForWriting() {
-  // Nothing to do for now.
+  assert(!NumCurrentElementsDeserializing && "deserializing when reading");
+  FinalizedForWriting = true;
 }
 
 /// Reads and return the signature record from \p PCH's control block, or
@@ -7328,6 +7329,12 @@ Decl *ASTReader::GetExternalDecl(uint32_t ID) {
 }
 
 void ASTReader::CompleteRedeclChain(const Decl *D) {
+  // We don't need to complete declaration chain after we start writing.
+  // We loses more chances to find ODR violation in the writing place and
+  // we get more efficient writing process.
+  if (FinalizedForWriting)
+    return;
+
   if (NumCurrentElementsDeserializing) {
     // We arrange to not care about the complete redeclaration chain while we're
     // deserializing. Just remember that the AST has marked this one as complete
diff --git a/clang/test/Modules/polluted-operator.cppm b/clang/test/Modules/polluted-operator.cppm
index b24464aa6ad21..9b45734432db9 100644
--- a/clang/test/Modules/polluted-operator.cppm
+++ b/clang/test/Modules/polluted-operator.cppm
@@ -51,7 +51,20 @@ module;
 export module b;
 import a;
 
+void b() {
+  std::variant<int, double> v;
+}
+
 // expected-error@* {{has different definitions in different modules; first difference is defined here found data member '_S_copy_ctor' with an initializer}}
 // expected-note@* {{but in 'a.<global>' found data member '_S_copy_ctor' with a different initializer}}
 // expected-error@* {{from module 'a.<global>' is not present in definition of 'variant<_Types...>' provided earlier}}
 // expected-note@* {{declaration of 'swap' does not match}}
+
+//--- c.cppm
+module;
+#include "bar.h"
+export module c;
+import a;
+
+// expected-error@* {{has different definitions in different modules; first difference is defined here found data member '_S_copy_ctor' with an initializer}}
+// expected-note@* {{but in 'a.<global>' found data member '_S_copy_ctor' with a different initializer}}