diff --git a/ChangeLog b/ChangeLog
index 941f7a111b..c7143225d4 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Sun Nov 30 09:35:14 2003  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* string.c (rb_str_update): get rid of SEGV at just allocated String.
+	  [ruby-core:01812]
+
 Fri Nov 28 23:19:34 2003  Yukihiro Matsumoto  <matz@ruby-lang.org>
 
 	* gc.c (gc_mark): explicitly check mark recursion levels, instead
diff --git a/string.c b/string.c
index eebc61cd10..d0ccce7671 100644
--- a/string.c
+++ b/string.c
@@ -1314,7 +1314,9 @@ rb_str_update(str, beg, len, val)
 	memmove(RSTRING(str)->ptr+beg, RSTRING(val)->ptr, RSTRING(val)->len);
     }
     RSTRING(str)->len += RSTRING(val)->len - len;
-    RSTRING(str)->ptr[RSTRING(str)->len] = '\0';
+    if (RSTRING(str)->ptr) {
+	RSTRING(str)->ptr[RSTRING(str)->len] = '\0';
+    }
     OBJ_INFECT(str, val);
 }