diff --git a/clang/include/clang/Basic/SourceManager.h b/clang/include/clang/Basic/SourceManager.h
--- a/clang/include/clang/Basic/SourceManager.h
+++ b/clang/include/clang/Basic/SourceManager.h
@@ -1825,7 +1825,13 @@
   /// specified SourceLocation offset.  This is a very hot method.
   inline bool isOffsetInFileID(FileID FID,
                                SourceLocation::UIntTy SLocOffset) const {
-    const SrcMgr::SLocEntry &Entry = getSLocEntry(FID);
+    bool Invalid = false;
+    const SrcMgr::SLocEntry &Entry = getSLocEntry(FID, &Invalid);
+
+    // If the entry is invalid, it can't contain it.
+    if (Invalid)
+      return false;
+
     // If the entry is after the offset, it can't contain it.
     if (SLocOffset < Entry.getOffset()) return false;