diff --git a/ChangeLog b/ChangeLog
index 686ba4510a..2cccfd1cc7 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,8 @@
 Fri Mar 21 01:29:35 2003  Yukihiro Matsumoto  <matz@ruby-lang.org>
 
+	* sprintf.c (rb_f_sprintf): copy sign bits only if value is
+	  negative.
+
 	* missing.h: include <stdarg.h> or <varargs.h> if HAVE_VSNPRINTF
 	  is not defined.
 
diff --git a/sprintf.c b/sprintf.c
index 69f9fa3ff3..caea4c587f 100644
--- a/sprintf.c
+++ b/sprintf.c
@@ -556,7 +556,12 @@ rb_f_sprintf(argc, argv)
 		    }
 		}
 		else {
-		    char c = sign_bits(base, p);
+		    char c;
+
+		    if (bignum && !RBIGNUM(val)->sign)
+			c = sign_bits(base, p);
+		    else
+			c = '0';
 		    while (len < prec--) {
 			buf[blen++] = c;
 		    }