Index: lib/Serialization/ASTWriter.cpp
===================================================================
--- lib/Serialization/ASTWriter.cpp
+++ lib/Serialization/ASTWriter.cpp
@@ -5711,6 +5711,8 @@
 }
 
 void ASTWriter::ResolvedExceptionSpec(const FunctionDecl *FD) {
+  if (FD->isFromASTFile())
+    return ;
   assert(!DoneWritingDeclsAndTypes && "Already done writing updates!");
   if (!Chain) return;
   Chain->forEachImportedKeyDecl(FD, [&](const Decl *D) {