Index: lib/Target/X86/Disassembler/X86DisassemblerDecoder.cpp
===================================================================
--- lib/Target/X86/Disassembler/X86DisassemblerDecoder.cpp
+++ lib/Target/X86/Disassembler/X86DisassemblerDecoder.cpp
@@ -980,6 +980,15 @@
       insn->opcode == 0xE3)
     attrMask ^= ATTR_ADSIZE;
 
+  /*
+   * CALL 64-bit mode hack to ignore opcode size prefix when disassembling
+   * and consume all 4 bytes of the immediate instead;
+   * NOTE: intel spec states CALL rel16 is N.S. in 64-bit mode
+   */
+  if (insn->mode == MODE_64BIT && insn->opcodeType == ONEBYTE &&
+      insn->opcode == 0xE8 && isPrefixAtLocation(insn, 0x66, insn->necessaryPrefixLocation))
+    attrMask ^= ATTR_OPSIZE;
+
   if (getIDWithAttrMask(&instructionID, insn, attrMask))
     return -1;
 
Index: test/MC/Disassembler/X86/x86-64.txt
===================================================================
--- test/MC/Disassembler/X86/x86-64.txt
+++ test/MC/Disassembler/X86/x86-64.txt
@@ -301,3 +301,9 @@
 
 # CHECK: movq %rax, 1515870810
 0x67, 0x48 0xa3 0x5a 0x5a 0x5a 0x5a
+
+# CHECK: callq -32769
+0x66 0xe8 0xff 0x7f 0xff 0xff
+
+# CHECK: callq -32769
+0x66 0x66 0x48 0xe8 0xff 0x7f 0xff 0xff