diff --git a/disassembler/disassembler_x86.cc b/disassembler/disassembler_x86.cc
index e12559f..b9e98f6 100644
--- a/disassembler/disassembler_x86.cc
+++ b/disassembler/disassembler_x86.cc
@@ -508,7 +508,7 @@
           case 0x5D: opcode << "min"; break;
           case 0x5E: opcode << "div"; break;
           case 0x5F: opcode << "max"; break;
-          default: LOG(FATAL) << "Unreachable";
+          default: LOG(FATAL) << "Unreachable"; UNREACHABLE();
         }
         if (prefix[2] == 0x66) {
           opcode << "pd";
@@ -1239,7 +1239,7 @@
     case 0xF2: prefixed_opcode << "repne "; break;
     case 0xF3: prefixed_opcode << "repe "; break;
     case 0: break;
-    default: LOG(FATAL) << "Unreachable";
+    default: LOG(FATAL) << "Unreachable"; UNREACHABLE();
   }
   prefixed_opcode << opcode.str();
   os << FormatInstructionPointer(begin_instr)