diff --git a/clang/lib/Serialization/ASTReader.cpp b/clang/lib/Serialization/ASTReader.cpp
index 55bec61..55f2be3 100644
--- a/clang/lib/Serialization/ASTReader.cpp
+++ b/clang/lib/Serialization/ASTReader.cpp
@@ -1523,9 +1523,9 @@
     if (Record[3])
       FileInfo.setHasLineDirectives();
 
-    const DeclID *FirstDecl = F->FileSortedDecls + Record[6];
     unsigned NumFileDecls = Record[7];
     if (NumFileDecls && ContextObj) {
+      const DeclID *FirstDecl = F->FileSortedDecls + Record[6];
       assert(F->FileSortedDecls && "FILE_SORTED_DECLS not encountered yet ?");
       FileDeclIDs[FID] = FileDeclsInfo(F, llvm::makeArrayRef(FirstDecl,
                                                              NumFileDecls));