diff --git a/src/parser.c b/src/parser.c
index 5effb219e..de7e82dc2 100644
--- a/src/parser.c
+++ b/src/parser.c
@@ -2350,7 +2350,7 @@ static bool parse_variable_member(rbs_parser_t *parser, rbs_position_t comment_p
         if (parser->next_token.type == tAIDENT || parser->next_token.type == kATRBS) {
             rbs_parser_advance(parser);
         } else {
-            rbs_parser_set_error(parser, parser->current_token, false, "Unexpected error");
+            rbs_parser_set_error(parser, parser->next_token, true, "unexpected token for class instance variable name");
             return false;
         }
 
diff --git a/test/rbs/errors_test.rb b/test/rbs/errors_test.rb
index 6aed3fbb0..a152b5ba3 100644
--- a/test/rbs/errors_test.rb
+++ b/test/rbs/errors_test.rb
@@ -24,6 +24,29 @@ class Foo
     end
   end
 
+  def test_parse_signature_with_malformed_class_instance_variable
+    ["class M self.", "module M self.", "class M self.5", %q{class M self."x"}].each do |source|
+      assert_raises RBS::ParsingError, "#{source.inspect} should raise RBS::ParsingError" do
+        RBS::Parser.parse_signature(buffer(source))
+      end
+    end
+  end
+
+  def test_parse_signature_with_malformed_class_instance_variable_detailed_message
+    omit "Exception#detailed_message does not supported" unless Exception.method_defined?(:detailed_message)
+
+    assert_raises RBS::ParsingError do
+      RBS::Parser.parse_signature(buffer("class M self.5"))
+    end.tap do |exn|
+      assert_equal <<~DETAILED_MESSAGE, exn.detailed_message
+        test.rbs:1:13...1:14: Syntax error: unexpected token for class instance variable name, token=`5` (tINTEGER) (RBS::ParsingError)
+
+          class M self.5
+                       ^
+      DETAILED_MESSAGE
+    end
+  end
+
   def test_parse_type_with_parsing_error_detailed_message
     omit "Exception#detailed_message does not supported" unless Exception.method_defined?(:detailed_message)