diff --git a/util/m5/m5op_x86.S b/util/m5/m5op_x86.S
index 5f746459f..93eacc24d 100644
--- a/util/m5/m5op_x86.S
+++ b/util/m5/m5op_x86.S
@@ -55,6 +55,7 @@ TWO_BYTE_OP(m5_dump_stats, dumpstats_func)
 TWO_BYTE_OP(m5_dumpreset_stats, dumprststats_func)
 TWO_BYTE_OP(m5_checkpoint, ckpt_func)
 TWO_BYTE_OP(m5_readfile, readfile_func)
+TWO_BYTE_OP(m5_writefile, writefile_func)
 TWO_BYTE_OP(m5_debugbreak, debugbreak_func)
 TWO_BYTE_OP(m5_switchcpu, switchcpu_func)
 TWO_BYTE_OP(m5_addsymbol, addsymbol_func)