diff --git a/src/arch/sparc/isa/decoder.isa b/src/arch/sparc/isa/decoder.isa
index e2d1707dd..2ce700ef1 100644
--- a/src/arch/sparc/isa/decoder.isa
+++ b/src/arch/sparc/isa/decoder.isa
@@ -1011,13 +1011,15 @@ decode OP default Unknown::unknown()
             }
             // M5 special opcodes use the reserved IMPDEP2A opcode space
             0x37: decode M5FUNC {
+#if FULL_SYSTEM
                 // we have 7 bits of space here to play with...
                 0x21: m5exit({{PseudoInst::m5exit(xc->tcBase(), O0);
                               }}, No_OpClass, IsNonSpeculative);
                 0x54: m5panic({{
                               panic("M5 panic instruction called at pc=%#x.", xc->readPC());
                               }}, No_OpClass, IsNonSpeculative);
-
+#endif
+                default: Trap::impdep2({{fault = new IllegalInstruction;}});
             }
             0x38: Branch::jmpl({{
                 Addr target = Rs1 + Rs2_or_imm13;