diff --git a/lib/Serialization/ASTWriter.cpp b/lib/Serialization/ASTWriter.cpp
index 5257859..2afdc32 100644
--- a/lib/Serialization/ASTWriter.cpp
+++ b/lib/Serialization/ASTWriter.cpp
@@ -3729,6 +3729,12 @@
   if (D == 0) {
     return 0;
   }
+  
+  // If D comes from an AST file, its declaration ID is already known and
+  // fixed.
+  if (D->isFromASTFile())
+    return D->getGlobalID();
+  
   assert(!(reinterpret_cast<uintptr_t>(D) & 0x01) && "Invalid decl pointer");
   DeclID &ID = DeclIDs[D];
   if (ID == 0) {
@@ -3745,6 +3751,11 @@
   if (D == 0)
     return 0;
 
+  // If D comes from an AST file, its declaration ID is already known and
+  // fixed.
+  if (D->isFromASTFile())
+    return D->getGlobalID();
+
   assert(DeclIDs.find(D) != DeclIDs.end() && "Declaration not emitted!");
   return DeclIDs[D];
 }
@@ -4273,10 +4284,6 @@
     StoredIdx = Idx;
 }
 
-void ASTWriter::DeclRead(DeclID ID, const Decl *D) {
-  DeclIDs[D] = ID;
-}
-
 void ASTWriter::SelectorRead(SelectorID ID, Selector S) {
   SelectorIDs[S] = ID;
 }
diff --git a/lib/Serialization/ASTWriterDecl.cpp b/lib/Serialization/ASTWriterDecl.cpp
index f6c65f0..19d8372 100644
--- a/lib/Serialization/ASTWriterDecl.cpp
+++ b/lib/Serialization/ASTWriterDecl.cpp
@@ -1679,12 +1679,18 @@
     VisibleOffset = WriteDeclContextVisibleBlock(Context, DC);
   }
 
-  // Determine the ID for this declaration
-  serialization::DeclID &IDR = DeclIDs[D];
-  if (IDR == 0)
-    IDR = NextDeclID++;
-  serialization::DeclID ID = IDR;
-
+  // Determine the ID for this declaration.
+  serialization::DeclID ID;
+  if (D->isFromASTFile())
+    ID = getDeclID(D);
+  else {
+    serialization::DeclID &IDR = DeclIDs[D];
+    if (IDR == 0)
+      IDR = NextDeclID++;
+    
+    ID= IDR;
+  }
+  
   if (ID < FirstDeclID) {
     // We're replacing a decl in a previous file.
     ReplacedDecls.push_back(ReplacedDeclInfo(ID, Stream.GetCurrentBitNo(),