diff --git a/src/debugger.h b/src/debugger.h
index 542a006..4c0c1b6 100644
--- a/src/debugger.h
+++ b/src/debugger.h
@@ -189,7 +189,7 @@
   static bool IsSuspended(JDWP::ObjectId threadId);
   //static void WaitForSuspend(JDWP::ObjectId threadId);
 
-  // Fills 'thread_ids' with the threads in the given thread group. If thread_group_id == NULL,
+  // Fills 'thread_ids' with the threads in the given thread group. If thread_group_id == 0,
   // returns all threads.
   static void GetThreads(JDWP::ObjectId thread_group_id, std::vector<JDWP::ObjectId>& thread_ids);
   static void GetChildThreadGroups(JDWP::ObjectId thread_group_id, std::vector<JDWP::ObjectId>& child_thread_group_ids);
diff --git a/src/jdwp/jdwp_handler.cc b/src/jdwp/jdwp_handler.cc
index 7a796fe..36fbaf1 100644
--- a/src/jdwp/jdwp_handler.cc
+++ b/src/jdwp/jdwp_handler.cc
@@ -209,7 +209,7 @@
  */
 static JdwpError VM_AllThreads(JdwpState*, const uint8_t*, int, ExpandBuf* pReply) {
   std::vector<ObjectId> thread_ids;
-  Dbg::GetThreads(NULL, thread_ids);
+  Dbg::GetThreads(0, thread_ids);
 
   expandBufAdd4BE(pReply, thread_ids.size());
   for (uint32_t i = 0; i < thread_ids.size(); ++i) {