diff --git a/disassembler/disassembler.cc b/disassembler/disassembler.cc
index c05c3ed..6334717 100644
--- a/disassembler/disassembler.cc
+++ b/disassembler/disassembler.cc
@@ -42,7 +42,7 @@
     return new x86::DisassemblerX86(options, true);
   } else {
     UNIMPLEMENTED(FATAL) << "no disassembler for " << instruction_set;
-    return NULL;
+    return nullptr;
   }
 }