diff --git a/lib/rdoc/known_classes.rb b/lib/rdoc/known_classes.rb
index bdda96ae0e..3e8752bbde 100644
--- a/lib/rdoc/known_classes.rb
+++ b/lib/rdoc/known_classes.rb
@@ -46,8 +46,8 @@ module RDoc
     "rb_eInterrupt"        => "Interrupt",
     "rb_eLoadError"        => "LoadError",
     "rb_eNameError"        => "NameError",
-    "rb_eNoMemError"       => "NoMemError",
-    "rb_eNotImpError"      => "NotImpError",
+    "rb_eNoMemError"       => "NoMemoryError",
+    "rb_eNotImpError"      => "NotImplementedError",
     "rb_eRangeError"       => "RangeError",
     "rb_eRuntimeError"     => "RuntimeError",
     "rb_eScriptError"      => "ScriptError",
@@ -58,7 +58,7 @@ module RDoc
     "rb_eSystemCallError"  => "SystemCallError",
     "rb_eSystemExit"       => "SystemExit",
     "rb_eTypeError"        => "TypeError",
-    "rb_eZeroDivError"     => "ZeroDivError",
+    "rb_eZeroDivError"     => "ZeroDivisionError",
 
     "rb_mComparable"       => "Comparable",
     "rb_mEnumerable"       => "Enumerable",
diff --git a/test/rdoc/test_rdoc_parser_c.rb b/test/rdoc/test_rdoc_parser_c.rb
index 8125f5def6..4bb18ce925 100644
--- a/test/rdoc/test_rdoc_parser_c.rb
+++ b/test/rdoc/test_rdoc_parser_c.rb
@@ -101,6 +101,29 @@ class TestRDocParserC < RDoc::TestCase
     end
   end
 
+  def test_known_classes
+    RDoc::KNOWN_CLASSES.each do |var, name|
+      case name
+      when "Refinement"
+        next unless defined?(Refinement)
+      when "Bignum", "Fixnum", "Data", "Socket", /\A(?![A-Z])/
+        next
+      end
+      obj = Object.const_get(name)
+      assert_equal obj.name, name
+      case var
+      when /\Arb_c/
+        assert_kind_of Class, obj
+      when /\Arb_m/
+        assert_kind_of Module, obj
+      when /\Arb_e/
+        assert_operator obj, :<=, Exception
+      else
+        raise "unknown prefix: #{var} => #{name}"
+      end
+    end
+  end
+
   def test_initialize
     some_ext        = @top_level.add_class RDoc::NormalClass, 'SomeExt'
                       @top_level.add_class RDoc::SingleClass, 'SomeExtSingle'
@@ -115,8 +138,6 @@ class TestRDocParserC < RDoc::TestCase
 
     parser = RDoc::Parser::C.new @top_level, @fn, '', @options, @stats
 
-    assert_equal "ArgumentError", parser.known_classes["rb_eArgError"]
-
     expected = { 'cSomeExt' => some_ext }
     assert_equal expected, parser.classes