diff --git a/lib/Target/X86/AsmPrinter/X86ATTInstPrinter.cpp b/lib/Target/X86/AsmPrinter/X86ATTInstPrinter.cpp
index 1a35a4941c2..734a545555f 100644
--- a/lib/Target/X86/AsmPrinter/X86ATTInstPrinter.cpp
+++ b/lib/Target/X86/AsmPrinter/X86ATTInstPrinter.cpp
@@ -73,7 +73,7 @@ void X86ATTInstPrinter::printOperand(const MCInst *MI, unsigned OpNo) {
     O << '$' << Op.getImm();
     
     if (CommentStream && (Op.getImm() > 255 || Op.getImm() < -256))
-      *CommentStream << format("imm = 0x%X\n", Op.getImm());
+      *CommentStream << format("imm = 0x%llX\n", (long long)Op.getImm());
     
   } else {
     assert(Op.isExpr() && "unknown operand kind in printOperand");