diff --git a/clang/lib/Serialization/ASTReader.cpp b/clang/lib/Serialization/ASTReader.cpp
index 066261c0215b..6c5338a2dd52 100644
--- a/clang/lib/Serialization/ASTReader.cpp
+++ b/clang/lib/Serialization/ASTReader.cpp
@@ -8471,6 +8471,10 @@ void ASTReader::ReadComments() {
       }
     }
   NextCursor:
+    // De-serialized SourceLocations get negative FileIDs for other modules,
+    // potentially invalidating the original order. Sort it again.
+    std::sort(Comments.begin(), Comments.end(),
+              BeforeThanCompare<RawComment>(SourceMgr));
     Context.Comments.addDeserializedComments(Comments);
   }
 }