diff --git a/src/arch/alpha/isa/decoder.isa b/src/arch/alpha/isa/decoder.isa
index 584d64a3da..f5483d9c0c 100644
--- a/src/arch/alpha/isa/decoder.isa
+++ b/src/arch/alpha/isa/decoder.isa
@@ -762,7 +762,7 @@ decode OPCODE default Unknown::unknown() {
             1: hw_mtpr({{
                 int miscRegIndex = (ipr_index < NumInternalProcRegs) ?
                         IprToMiscRegIndex[ipr_index] : -1;
-                if(miscRegIndex < 0 || !IprIsWritable(miscRegIndex)
+                if(miscRegIndex < 0 || !IprIsWritable(miscRegIndex) ||
                     miscRegIndex >= NumInternalProcRegs)
                         fault = new UnimplementedOpcodeFault;
                 else