diff --git a/ChangeLog b/ChangeLog
index ee673a70c9..af066ae012 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+Sat Mar 19 17:14:46 2011  Tajima Akio <artonx@yahoo.co.jp>
+
+	* hash.c (ruby_setenv): checking with max process environment 
+	  block size fow Win32. 32767 for 2000/XP, 2003. if failed to
+	  read the block, then checking with 5120 for earlier Windows.
+
 Sat Mar 19 12:30:25 2011  Tanaka Akira  <akr@fsij.org>
 
 	* ext/openssl/ossl_x509revoked.c: parenthesize macro arguments.
diff --git a/hash.c b/hash.c
index f86152ae70..b303211db7 100644
--- a/hash.c
+++ b/hash.c
@@ -2206,7 +2206,12 @@ ruby_setenv(const char *name, const char *value)
 	rb_sys_fail("ruby_setenv");
     }
     if (value) {
-	if (strlen(value) > 5120) goto fail;
+	char* p = GetEnvironmentStringsA();
+	if (p) {
+            if (strlen(value) + strlen(p) >= 32767) goto fail;
+	} else {
+	    if (strlen(value) >= 5120) goto fail;
+	}
 	buf = rb_sprintf("%s=%s", name, value);
     }
     else {