Index: include/llvm/DebugInfo/PDB/Native/DbiStreamBuilder.h
===================================================================
--- include/llvm/DebugInfo/PDB/Native/DbiStreamBuilder.h
+++ include/llvm/DebugInfo/PDB/Native/DbiStreamBuilder.h
@@ -82,6 +82,7 @@
 
   Error finalize();
   uint32_t calculateModiSubstreamSize() const;
+  uint32_t calculateNamesOffset() const;
   uint32_t calculateSectionContribsStreamSize() const;
   uint32_t calculateSectionMapStreamSize() const;
   uint32_t calculateFileInfoSubstreamSize() const;
Index: lib/DebugInfo/PDB/Native/DbiStreamBuilder.cpp
===================================================================
--- lib/DebugInfo/PDB/Native/DbiStreamBuilder.cpp
+++ lib/DebugInfo/PDB/Native/DbiStreamBuilder.cpp
@@ -129,7 +129,7 @@
   return sizeof(SecMapHeader) + sizeof(SecMapEntry) * SectionMap.size();
 }
 
-uint32_t DbiStreamBuilder::calculateFileInfoSubstreamSize() const {
+uint32_t DbiStreamBuilder::calculateNamesOffset() const {
   uint32_t Size = 0;
   Size += sizeof(ulittle16_t);                         // NumModules
   Size += sizeof(ulittle16_t);                         // NumSourceFiles
@@ -139,6 +139,11 @@
   for (const auto &M : ModiList)
     NumFileInfos += M->source_files().size();
   Size += NumFileInfos * sizeof(ulittle32_t); // FileNameOffsets
+  return Size;
+}
+
+uint32_t DbiStreamBuilder::calculateFileInfoSubstreamSize() const {
+  uint32_t Size = calculateNamesOffset();
   Size += calculateNamesBufferSize();
   return alignTo(Size, sizeof(uint32_t));
 }
@@ -157,9 +162,8 @@
 
 Error DbiStreamBuilder::generateFileInfoSubstream() {
   uint32_t Size = calculateFileInfoSubstreamSize();
-  uint32_t NameSize = calculateNamesBufferSize();
   auto Data = Allocator.Allocate<uint8_t>(Size);
-  uint32_t NamesOffset = Size - NameSize;
+  uint32_t NamesOffset = calculateNamesOffset();
 
   FileInfoBuffer = MutableBinaryByteStream(MutableArrayRef<uint8_t>(Data, Size),
                                            llvm::support::little);
@@ -207,6 +211,9 @@
     }
   }
 
+  if (auto EC = NameBufferWriter.padToAlignment(sizeof(uint32_t)))
+    return EC;
+
   if (NameBufferWriter.bytesRemaining() > 0)
     return make_error<RawError>(raw_error_code::invalid_format,
                                 "The names buffer contained unexpected data.");