diff --git a/ChangeLog b/ChangeLog
index e09949b97c..47880da524 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Fri Dec  1 17:01:49 2006  NAKAMURA Usaku  <usa@ruby-lang.org>
+
+	* gc.c (ruby_init_stack): decrease "stack level too deep" in Windows.
+	  merge from trunk.
+
 Fri Dec  1 16:31:53 2006  Hidetoshi NAGAI  <nagai@ai.kyutech.ac.jp>
 
 	* ext/tk/tcltklib.c: shouldn't run the killed thread at callback.
diff --git a/gc.c b/gc.c
index ccfa68b23d..e3b088efd1 100644
--- a/gc.c
+++ b/gc.c
@@ -424,7 +424,7 @@ static unsigned int STACK_LEVEL_MAX = 65535;
 unsigned int _stacksize = 262144;
 # define STACK_LEVEL_MAX (_stacksize - 4096)
 # undef HAVE_GETRLIMIT
-#elif defined(HAVE_GETRLIMIT)
+#elif defined(HAVE_GETRLIMIT) || defined(_WIN32)
 static unsigned int STACK_LEVEL_MAX = 655300;
 #else
 # define STACK_LEVEL_MAX 655300
@@ -1542,6 +1542,19 @@ void ruby_init_stack(VALUE *addr
             STACK_LEVEL_MAX = (rlim.rlim_cur - space) / sizeof(VALUE);
         }
     }
+#elif defined _WIN32
+    {
+	MEMORY_BASIC_INFORMATION mi;
+	DWORD size;
+	DWORD space;
+
+	if (VirtualQuery(&mi, &mi, sizeof(mi))) {
+	    size = (char *)mi.BaseAddress - (char *)mi.AllocationBase;
+	    space = size / 5;
+	    if (space > 1024*1024) space = 1024*1024;
+	    STACK_LEVEL_MAX = (size - space) / sizeof(VALUE);
+	}
+    }
 #endif
 }