diff --git a/llvm/lib/Support/FileOutputBuffer.cpp b/llvm/lib/Support/FileOutputBuffer.cpp
index e6e4da3..df4ae93 100644
--- a/llvm/lib/Support/FileOutputBuffer.cpp
+++ b/llvm/lib/Support/FileOutputBuffer.cpp
@@ -77,6 +77,10 @@
   if (EC)
     return EC;
 
+  EC = sys::fs::resize_file(FD, Size);
+  if (EC)
+    return EC;
+
   auto MappedFile = llvm::make_unique<mapped_file_region>(
       FD, mapped_file_region::readwrite, Size, 0, EC);
   int Ret = close(FD);