2 files changed, 6 insertions, 0 deletions
diff --git a/string.c b/string.c
index e1bd9a052e..0c782a430f 100644
--- a/string.c
+++ b/string.c
@@ -4079,6 +4079,7 @@ 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);
diff --git a/test/ruby/test_string.rb b/test/ruby/test_string.rb
index ec90193546..75da42eeef 100644
--- a/test/ruby/test_string.rb
+++ b/test/ruby/test_string.rb
@@ -1872,6 +1872,11 @@ CODE
 
     assert_equal("!", " ".succ)
     assert_equal("", "".succ)
+
+    bug = '[ruby-core:83062] [Bug #13952]'
+    s = "\xff".b
+    assert_not_predicate(s, :ascii_only?)
+    assert_predicate(s.succ, :ascii_only?, bug)
   end
 
   def test_succ!