Index: llvm/lib/ObjectYAML/ELFYAML.cpp
===================================================================
--- llvm/lib/ObjectYAML/ELFYAML.cpp
+++ llvm/lib/ObjectYAML/ELFYAML.cpp
@@ -275,6 +275,7 @@
   ECase(ELFOSABI_C6000_LINUX);
   ECase(ELFOSABI_STANDALONE);
 #undef ECase
+  IO.enumFallback<Hex8>(Value);
 }
 
 void ScalarBitSetTraits<ELFYAML::ELF_EF>::bitset(IO &IO,
Index: llvm/test/tools/yaml2obj/ELF/header-osabi.yaml
===================================================================
--- llvm/test/tools/yaml2obj/ELF/header-osabi.yaml
+++ llvm/test/tools/yaml2obj/ELF/header-osabi.yaml
@@ -325,3 +325,16 @@
   Type:    ET_REL
   Machine: EM_X86_64
   OSABI:   ELFOSABI_STANDALONE
+
+## Test we can use an arbitrary number for OSABI.
+# RUN: yaml2obj %s --docnum=27 -o %t.number
+# RUN: llvm-readobj --file-headers %t.number | FileCheck %s --check-prefix=OSABI-NUMBER
+# OSABI-NUMBER: OS/ABI: 0xFE
+
+--- !ELF
+FileHeader:
+  Class:   ELFCLASS64
+  Data:    ELFDATA2LSB
+  Type:    ET_REL
+  Machine: EM_X86_64
+  OSABI:   0xFE