diff --git a/lib/Serialization/ASTCommon.h b/lib/Serialization/ASTCommon.h
index 36958c7..5ed607a 100644
--- a/lib/Serialization/ASTCommon.h
+++ b/lib/Serialization/ASTCommon.h
@@ -21,7 +21,8 @@
 namespace serialization {
 
 enum DeclUpdateKind {
-  UPD_CXX_SET_DEFINITIONDATA
+  UPD_CXX_SET_DEFINITIONDATA,
+  UPD_CXX_ADDED_IMPLICIT_MEMBER
 };
 
 TypeIdx TypeIdxFromBuiltin(const BuiltinType *BT);
diff --git a/lib/Serialization/ASTReaderDecl.cpp b/lib/Serialization/ASTReaderDecl.cpp
index f4568a7..7192195 100644
--- a/lib/Serialization/ASTReaderDecl.cpp
+++ b/lib/Serialization/ASTReaderDecl.cpp
@@ -1599,6 +1599,10 @@
       InitializeCXXDefinitionData(RD, DefinitionDecl, Record, Idx);
       break;
     }
+
+    case UPD_CXX_ADDED_IMPLICIT_MEMBER:
+      cast<CXXRecordDecl>(D)->addedMember(Reader.GetDecl(Record[Idx++]));
+      break;
     }
   }
 }
diff --git a/lib/Serialization/ASTWriter.cpp b/lib/Serialization/ASTWriter.cpp
index 436525f..340f0cc 100644
--- a/lib/Serialization/ASTWriter.cpp
+++ b/lib/Serialization/ASTWriter.cpp
@@ -3326,3 +3326,17 @@
     }
   }
 }
+
+void ASTWriter::AddedCXXImplicitMember(const CXXRecordDecl *RD, const Decl *D) {
+  assert(D->isImplicit());
+  if (!(D->getPCHLevel() == 0 && RD->getPCHLevel() > 0))
+    return; // Not a source member added to a class from PCH.
+  if (!isa<CXXMethodDecl>(D))
+    return; // We are interested in lazily declared implicit methods.
+
+  // A decl coming from PCH was modified.
+  assert(RD->isDefinition());
+  UpdateRecord &Record = DeclUpdates[RD];
+  Record.push_back(UPD_CXX_ADDED_IMPLICIT_MEMBER);
+  AddDeclRef(D, Record);
+}