Index: llvm/include/llvm/BinaryFormat/COFF.h
===================================================================
--- llvm/include/llvm/BinaryFormat/COFF.h
+++ llvm/include/llvm/BinaryFormat/COFF.h
@@ -572,6 +572,40 @@
   uint32_t NumberOfRvaAndSize;
 };
 
+struct PE32PlusHeader {
+  uint16_t Magic;
+  uint8_t MajorLinkerVersion;
+  uint8_t MinorLinkerVersion;
+  uint32_t SizeOfCode;
+  uint32_t SizeOfInitializedData;
+  uint32_t SizeOfUninitializedData;
+  uint32_t AddressOfEntryPoint; // RVA
+  uint32_t BaseOfCode;          // RVA
+  uint64_t ImageBase;
+  uint32_t SectionAlignment;
+  uint32_t FileAlignment;
+  uint16_t MajorOperatingSystemVersion;
+  uint16_t MinorOperatingSystemVersion;
+  uint16_t MajorImageVersion;
+  uint16_t MinorImageVersion;
+  uint16_t MajorSubsystemVersion;
+  uint16_t MinorSubsystemVersion;
+  uint32_t Win32VersionValue;
+  uint32_t SizeOfImage;
+  uint32_t SizeOfHeaders;
+  uint32_t CheckSum;
+  uint16_t Subsystem;
+  // FIXME: This should be DllCharacteristics to match the COFF spec.
+  uint16_t DLLCharacteristics;
+  uint64_t SizeOfStackReserve;
+  uint64_t SizeOfStackCommit;
+  uint64_t SizeOfHeapReserve;
+  uint64_t SizeOfHeapCommit;
+  uint32_t LoaderFlags;
+  // FIXME: This should be NumberOfRvaAndSizes to match the COFF spec.
+  uint32_t NumberOfRvaAndSize;
+};
+
 struct DataDirectory {
   uint32_t RelativeVirtualAddress;
   uint32_t Size;
Index: llvm/include/llvm/ObjectYAML/COFFYAML.h
===================================================================
--- llvm/include/llvm/ObjectYAML/COFFYAML.h
+++ llvm/include/llvm/ObjectYAML/COFFYAML.h
@@ -96,7 +96,7 @@
 };
 
 struct PEHeader {
-  COFF::PE32Header Header;
+  COFF::PE32PlusHeader Header;
   Optional<COFF::DataDirectory> DataDirectories[COFF::NUM_DATA_DIRECTORIES];
 };
 
Index: llvm/test/tools/yaml2obj/coff-arm64.yaml
===================================================================
--- llvm/test/tools/yaml2obj/coff-arm64.yaml
+++ llvm/test/tools/yaml2obj/coff-arm64.yaml
@@ -3,7 +3,9 @@
 # RUN: obj2yaml %t | FileCheck %s --check-prefix=ROUNDTRIP
 
 # CHECK: OptionalHeaderSize: 240
+# CHECK: ImageBase: 0x140000000
 
+# ROUNDTRIP: ImageBase: 5368709120
 # ROUNDTRIP: VirtualAddress:  4096
 # ROUNDTRIP: VirtualAddress:  8192
 # ROUNDTRIP: VirtualAddress:  12288
@@ -11,7 +13,7 @@
 --- !COFF
 OptionalHeader:  
   AddressOfEntryPoint: 4096
-  ImageBase:       1073741824
+  ImageBase:       5368709120
   SectionAlignment: 4096
   FileAlignment:   512
   MajorOperatingSystemVersion: 6