Index: lld/ELF/Driver.cpp
===================================================================
--- lld/ELF/Driver.cpp
+++ lld/ELF/Driver.cpp
@@ -501,6 +501,8 @@
     StringRef S = Arg->getValue();
     if (S == "binary")
       return true;
+    if (S.startswith("elf"))
+      return false;
     error("unknown --oformat value: " + S);
   }
   return false;
Index: lld/test/ELF/oformat-elf.s
===================================================================
--- /dev/null
+++ lld/test/ELF/oformat-elf.s
@@ -0,0 +1,19 @@
+# REQUIRES: x86
+# RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t
+
+# RUN: ld.lld -o %t.out %t --oformat elf64-x86-64
+# RUN: od -t x1 -v %t.out | FileCheck %s
+# CHECK: 0000000 7f 45 4c 46 02 01 01 00 00 00 00 00 00 00 00 00
+# CHECK: 0010000 90 11 22 cc cc cc cc cc cc cc cc cc cc cc cc cc
+
+.text
+.align 4
+.globl _start
+_start:
+ nop
+
+.section        .mysec.1,"ax"
+.byte   0x11
+
+.section        .mysec.2,"ax"
+.byte   0x22