Index: lib/Object/COFFImportFile.cpp
===================================================================
--- lib/Object/COFFImportFile.cpp
+++ lib/Object/COFFImportFile.cpp
@@ -496,7 +496,7 @@
 
   // COFF Header
   coff_file_header Header{
-      u16(0),
+      u16(Machine),
       u16(NumberOfSections),
       u32(0),
       u32(sizeof(Header) + (NumberOfSections * sizeof(coff_section))),
Index: test/tools/llvm-dlltool/coff-weak-exports.def
===================================================================
--- test/tools/llvm-dlltool/coff-weak-exports.def
+++ test/tools/llvm-dlltool/coff-weak-exports.def
@@ -1,5 +1,6 @@
 ; RUN: llvm-dlltool -m i386:x86-64 --input-def %s --output-lib %t.a
 ; RUN: llvm-nm %t.a | FileCheck %s
+; RUN: llvm-readobj %t.a | FileCheck -check-prefix=ARCH %s
 
 LIBRARY test.dll
 EXPORTS
@@ -26,3 +27,5 @@
 ; CHECK-NEXT: W __imp_ImpLibName2
 ; CHECK:      T ImpLibName3
 ; CHECK-NEXT: T __imp_ImpLibName3
+
+; ARCH-NOT: unknown arch