diff --git a/lib/rexml/parsers/baseparser.rb b/lib/rexml/parsers/baseparser.rb
index 5688c773..bbdcfc6c 100644
--- a/lib/rexml/parsers/baseparser.rb
+++ b/lib/rexml/parsers/baseparser.rb
@@ -318,7 +318,11 @@ def pull_event
               raise REXML::ParseException.new( "Bad ELEMENT declaration!", @source ) if md.nil?
               return [ :elementdecl, "<!ELEMENT" + md[1] ]
             elsif @source.match("ENTITY", true)
-              match = [:entitydecl, *@source.match(Private::ENTITYDECL_PATTERN, true, term: Private::ENTITY_TERM).captures.compact]
+              match_data = @source.match(Private::ENTITYDECL_PATTERN, true, term: Private::ENTITY_TERM)
+              unless match_data
+                raise REXML::ParseException.new("Malformed entity declaration", @source)
+              end
+              match = [:entitydecl, *match_data.captures.compact]
               ref = false
               if match[1] == '%'
                 ref = true
diff --git a/test/parse/test_entity_declaration.rb b/test/parse/test_entity_declaration.rb
index 7d750b90..72f26afe 100644
--- a/test/parse/test_entity_declaration.rb
+++ b/test/parse/test_entity_declaration.rb
@@ -1,9 +1,13 @@
 # frozen_string_literal: false
-require 'test/unit'
-require 'rexml/document'
+require "test/unit"
+require "core_assertions"
+
+require "rexml/document"
 
 module REXMLTests
   class TestParseEntityDeclaration < Test::Unit::TestCase
+    include Test::Unit::CoreAssertions
+
     private
     def xml(internal_subset)
       <<-XML
@@ -18,6 +22,7 @@ def parse(internal_subset)
       REXML::Document.new(xml(internal_subset)).doctype
     end
 
+    public
     def test_empty
       exception = assert_raise(REXML::ParseException) do
         parse(<<-INTERNAL_SUBSET)
@@ -25,18 +30,18 @@ def test_empty
         INTERNAL_SUBSET
       end
       assert_equal(<<-DETAIL.chomp, exception.to_s)
-Malformed notation declaration: name is missing
+Malformed entity declaration
 Line: 5
-Position: 72
+Position: 70
 Last 80 unconsumed characters:
- <!ENTITY>  ]> <r/>
+>  ]> <r/> 
       DETAIL
     end
 
     def test_linear_performance_gt
       seq = [10000, 50000, 100000, 150000, 200000]
       assert_linear_performance(seq, rehearsal: 10) do |n|
-        REXML::Document.new('<!DOCTYPE rubynet [<!ENTITY rbconfig.ruby_version "' + '>' * n + '">')
+        REXML::Document.new('<!DOCTYPE rubynet [<!ENTITY rbconfig.ruby_version "' + '>' * n + '">]>')
       end
     end
   end