diff --git a/ChangeLog b/ChangeLog
index 6393b68348..87f22ba702 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Sun Jan 24 13:55:54 2010  Tanaka Akira  <akr@fsij.org>
+
+	* string.c (rb_enc_strlen_cr): increment by rb_enc_mbminlen(enc) for
+	  broken byte sequence.  [ruby-core:27748]
+
 Sun Jan 24 05:18:34 2010  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* thread.c (thread_start_func_2): unlock all locking mutexes
diff --git a/string.c b/string.c
index 0bd1ca80cc..6addc621ee 100644
--- a/string.c
+++ b/string.c
@@ -1008,7 +1008,10 @@ rb_enc_strlen_cr(const char *p, const char *e, rb_encoding *enc, int *cr)
 	}
 	else {
 	    *cr = ENC_CODERANGE_BROKEN;
-	    p++;
+            if (p + rb_enc_mbminlen(enc) <= e)
+                p += rb_enc_mbminlen(enc);
+            else
+                p = e;
 	}
     }
     if (!*cr) *cr = ENC_CODERANGE_7BIT;