diff -r 8824bca93c38 -r cfa5b6f948f7 src/arch/x86/isa/formats/monitor_mwait.isa
--- a/src/arch/x86/isa/formats/monitor_mwait.isa	Mon Mar 30 16:25:48 2015 -0500
+++ b/src/arch/x86/isa/formats/monitor_mwait.isa	Tue Mar 31 09:02:03 2015 -0500
@@ -112,9 +112,9 @@
     {
         std::stringstream response;
 
+        // Although mwait could take hints from eax and ecx, the _srcRegIdx
+        // is not set, and thus should not be printed here
         printMnemonic(response, mnemonic);
-        ccprintf(response, " ");
-        printReg(response, _srcRegIdx[0], machInst.opSize);
         return response.str();
     }
 }};