1 files changed, 1 insertions, 0 deletions
diff --git a/string.c b/string.c
index ab798065d1..221d50eedf 100644
--- a/string.c
+++ b/string.c
@@ -3969,6 +3969,7 @@ str_succ(VALUE str)
             }
             carry_pos = s - sbeg;
 	}
+	ENC_CODERANGE_SET(str, ENC_CODERANGE_UNKNOWN);
     }
     RESIZE_CAPA(str, slen + carry_len);
     sbeg = RSTRING_PTR(str);