diff --git a/re.c b/re.c
index 5030519fc9..fdccea434a 100644
--- a/re.c
+++ b/re.c
@@ -1883,6 +1883,7 @@ match_captures(VALUE match)
 static int
 name_to_backref_number(struct re_registers *regs, VALUE regexp, const char* name, const char* name_end)
 {
+    if (NIL_P(regexp)) return -1;
     return onig_name_to_backref_number(RREGEXP_PTR(regexp),
 	(const unsigned char *)name, (const unsigned char *)name_end, regs);
 }
diff --git a/test/ruby/test_regexp.rb b/test/ruby/test_regexp.rb
index a22975dbd0..fe271dc3d7 100644
--- a/test/ruby/test_regexp.rb
+++ b/test/ruby/test_regexp.rb
@@ -156,6 +156,10 @@ class TestRegexp < Test::Unit::TestCase
     s = "foo"
     s[/(?<bar>o)/, "bar"] = "baz"
     assert_equal("fbazo", s)
+
+    /.*/ =~ "abc"
+    "a".sub("a", "")
+    assert_raise(IndexError) {Regexp.last_match(:_id)}
   end
 
   def test_named_capture_with_nul
diff --git a/version.h b/version.h
index 76a8079afb..7fa77863eb 100644
--- a/version.h
+++ b/version.h
@@ -1,6 +1,6 @@
 #define RUBY_VERSION "2.5.8"
 #define RUBY_RELEASE_DATE "2020-03-31"
-#define RUBY_PATCHLEVEL 214
+#define RUBY_PATCHLEVEL 215
 
 #define RUBY_RELEASE_YEAR 2020
 #define RUBY_RELEASE_MONTH 3