diff --git a/clang/lib/Basic/SourceManager.cpp b/clang/lib/Basic/SourceManager.cpp
--- a/clang/lib/Basic/SourceManager.cpp
+++ b/clang/lib/Basic/SourceManager.cpp
@@ -880,6 +880,8 @@
   for (NumProbes = 0; NumProbes < 8; ++NumProbes, ++I) {
     // Make sure the entry is loaded!
     const SrcMgr::SLocEntry &E = getLoadedSLocEntry(I);
+    if (E.getOffset() == 0)
+      return FileID(); // invalid entry.
     if (E.getOffset() <= SLocOffset) {
       FileID Res = FileID::get(-int(I) - 2);
       LastFileIDLookup = Res;