diff --git a/ChangeLog b/ChangeLog
index 21a5c985eb..ecd75c4d5b 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Wed Jan 12 19:37:10 2011  Tanaka Akira  <akr@fsij.org>
+
+	* vm_dump.c: parenthesize macro arguments.
+
 Wed Jan 12 19:28:23 2011  Tanaka Akira  <akr@fsij.org>
 
 	* vm.c (thread_free): reset ruby_current_thread if it points the
diff --git a/vm_dump.c b/vm_dump.c
index 741b4adc89..e27a64c563 100644
--- a/vm_dump.c
+++ b/vm_dump.c
@@ -16,7 +16,7 @@
 #define MAX_POSBUF 128
 
 #define VM_CFP_CNT(th, cfp) \
-  ((rb_control_frame_t *)(th->stack + th->stack_size) - (rb_control_frame_t *)(cfp))
+  ((rb_control_frame_t *)((th)->stack + (th)->stack_size) - (rb_control_frame_t *)(cfp))
 
 static void
 control_frame_dump(rb_thread_t *th, rb_control_frame_t *cfp)