diff --git a/ChangeLog b/ChangeLog
index f5b7547940..dde29576c1 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Thu Mar 27 03:26:40 2003  Nobuyoshi Nakada  <nobu.nokada@softhome.net>
+
+	* string.c (rb_str_capitalize_bang): check length before upcase
+	  first character.  (ruby-bugs:PR#697)
+
 Wed Mar 26 20:25:10 2003  Nobuyoshi Nakada  <nobu.nokada@softhome.net>
 
 	* dln.c (dln_find_1): break if path list end, even for too long
diff --git a/string.c b/string.c
index a273400d89..02abb90b07 100644
--- a/string.c
+++ b/string.c
@@ -2092,6 +2092,7 @@ rb_str_capitalize_bang(str)
     int modify = 0;
 
     rb_str_modify(str);
+    if (RSTRING(str)->len == 0 || !RSTRING(str)->ptr) return Qnil;
     s = RSTRING(str)->ptr; send = s + RSTRING(str)->len;
     if (ISLOWER(*s)) {
 	*s = toupper(*s);