diff --git a/clang/lib/CodeGen/CGDebugInfo.cpp b/clang/lib/CodeGen/CGDebugInfo.cpp
index 4c43c00..f436cab 100644
--- a/clang/lib/CodeGen/CGDebugInfo.cpp
+++ b/clang/lib/CodeGen/CGDebugInfo.cpp
@@ -422,8 +422,12 @@
   }
 
   SmallString<32> Checksum;
+
+  // Compute the checksum if possible. If the location is affected by a #line
+  // directive that refers to a file, PLoc will have an invalid FileID, and we
+  // will correctly get no checksum.
   Optional<llvm::DIFile::ChecksumKind> CSKind =
-      computeChecksum(SM.getFileID(Loc), Checksum);
+      computeChecksum(PLoc.getFileID(), Checksum);
   Optional<llvm::DIFile::ChecksumInfo<StringRef>> CSInfo;
   if (CSKind)
     CSInfo.emplace(*CSKind, Checksum);