diff --git a/signal.c b/signal.c
index 2e69cf08ac..b9bd3a5bb7 100644
--- a/signal.c
+++ b/signal.c
@@ -1022,11 +1022,11 @@ void
 rb_trap_exit(void)
 {
     rb_vm_t *vm = GET_VM();
-    VALUE trap_exit = vm->trap_list[0].cmd;
+    VALUE trap_exit = vm->trap_list.cmd[0];
 
     if (trap_exit) {
-	vm->trap_list[0].cmd = 0;
-	signal_exec(trap_exit, vm->trap_list[0].safe, 0);
+	vm->trap_list.cmd[0] = 0;
+	signal_exec(trap_exit, vm->trap_list.safe[0], 0);
     }
 }
 
@@ -1034,8 +1034,8 @@ void
 rb_signal_exec(rb_thread_t *th, int sig)
 {
     rb_vm_t *vm = GET_VM();
-    VALUE cmd = vm->trap_list[sig].cmd;
-    int safe = vm->trap_list[sig].safe;
+    VALUE cmd = vm->trap_list.cmd[sig];
+    int safe = vm->trap_list.safe[sig];
 
     if (cmd == 0) {
 	switch (sig) {
@@ -1237,7 +1237,7 @@ trap(int sig, sighandler_t func, VALUE command)
     rb_vm_t *vm = GET_VM();
 
     /*
-     * Be careful. ruby_signal() and trap_list[sig].cmd must be changed
+     * Be careful. ruby_signal() and trap_list.cmd[sig] must be changed
      * atomically. In current implementation, we only need to don't call
      * RUBY_VM_CHECK_INTS().
      */
@@ -1248,7 +1248,7 @@ trap(int sig, sighandler_t func, VALUE command)
 	oldfunc = ruby_signal(sig, func);
 	if (oldfunc == SIG_ERR) rb_sys_fail_str(rb_signo2signm(sig));
     }
-    oldcmd = vm->trap_list[sig].cmd;
+    oldcmd = vm->trap_list.cmd[sig];
     switch (oldcmd) {
       case 0:
       case Qtrue:
@@ -1264,8 +1264,8 @@ trap(int sig, sighandler_t func, VALUE command)
 	break;
     }
 
-    vm->trap_list[sig].cmd = command;
-    vm->trap_list[sig].safe = rb_safe_level();
+    vm->trap_list.cmd[sig] = command;
+    vm->trap_list.safe[sig] = rb_safe_level();
 
     return oldcmd;
 }
@@ -1422,7 +1422,7 @@ init_sigchld(int sig)
 	ruby_signal(sig, oldfunc);
     }
     else {
-	GET_VM()->trap_list[sig].cmd = 0;
+	GET_VM()->trap_list.cmd[sig] = 0;
     }
     return 0;
 }
diff --git a/vm.c b/vm.c
index 814f8b6780..6815e84f76 100644
--- a/vm.c
+++ b/vm.c
@@ -2115,8 +2115,6 @@ void rb_vm_trace_mark_event_hooks(rb_hook_list_t *hooks);
 void
 rb_vm_mark(void *ptr)
 {
-    int i;
-
     RUBY_MARK_ENTER("vm");
     RUBY_GC_INFO("-------------------------------------------------\n");
     if (ptr) {
@@ -2144,10 +2142,7 @@ rb_vm_mark(void *ptr)
 
 	rb_vm_trace_mark_event_hooks(&vm->event_hooks);
 
-	for (i = 0; i < RUBY_NSIG; i++) {
-	    if (vm->trap_list[i].cmd)
-		rb_gc_mark(vm->trap_list[i].cmd);
-	}
+	rb_gc_mark_values(RUBY_NSIG, vm->trap_list.cmd);
     }
 
     RUBY_MARK_LEAVE("vm");
diff --git a/vm_core.h b/vm_core.h
index c23f50690e..37241b36b0 100644
--- a/vm_core.h
+++ b/vm_core.h
@@ -547,9 +547,9 @@ typedef struct rb_vm_struct {
 
     /* signal */
     struct {
-	VALUE cmd;
-	int safe;
-    } trap_list[RUBY_NSIG];
+	VALUE cmd[RUBY_NSIG];
+	unsigned char safe[RUBY_NSIG];
+    } trap_list;
 
     /* hook */
     rb_hook_list_t event_hooks;