diff --git a/ChangeLog b/ChangeLog
index 75ed7788a8..b26b0f0524 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Mon Jun 12 22:25:09 2006  Yukihiro Matsumoto  <matz@ruby-lang.org>
+
+	* sprintf.c (rb_f_sprintf): adjust precision length to prevent
+	  splitting multi-byte characters.  [ruby-list:42389]
+
 Sun Jun 11 23:20:07 2006  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* lib/optparse.rb (OptionParser::Arguable#getopts): pass self to the
diff --git a/sprintf.c b/sprintf.c
index 5e85d9522f..3c0bc5cd2b 100644
--- a/sprintf.c
+++ b/sprintf.c
@@ -13,6 +13,7 @@
 **********************************************************************/
 
 #include "ruby.h"
+#include "re.h"
 #include <ctype.h>
 #include <math.h>
 
@@ -413,6 +414,23 @@ rb_f_sprintf(argc, argv)
 			len = prec;
 		    }
 		}
+		{
+		    char *s, *send;
+		    long l;
+
+			s = RSTRING(str)->ptr;
+			send = s + RSTRING(str)->len;
+			l = 0;
+			while (s < send) {
+			    long n = mbclen(*s);
+			    if (l + n > len) {
+				len = l;
+				break;
+			    }
+			    l += n;
+			    s += n;
+			}
+		}
 		if (flags&FWIDTH) {
 		    if (width > len) {
 			CHECK(width);