diff --git a/lib/error_highlight/core_ext.rb b/lib/error_highlight/core_ext.rb
index e6cacba..1cfc331 100644
--- a/lib/error_highlight/core_ext.rb
+++ b/lib/error_highlight/core_ext.rb
@@ -24,7 +24,7 @@ module CoreExt
               _, _, snippet, highlight = ErrorHighlight.formatter.message_for(spot).lines
               out += "\n    | #{ snippet }      #{ highlight }"
             else
-              out += "\n    (cannot highlight method definition; try Ruby 3.5 or later)"
+              out += "\n    (cannot highlight method definition; try Ruby 4.0 or later)"
             end
           end
           ret << "\n" + out if out
diff --git a/test/test_error_highlight.rb b/test/test_error_highlight.rb
index 43e2320..1276a0a 100644
--- a/test/test_error_highlight.rb
+++ b/test/test_error_highlight.rb
@@ -1468,7 +1468,7 @@ def test_wrong_number_of_arguments_for_method
       MethodDefLocationSupported ?
    "|   def wrong_number_of_arguments_test(x, y)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^" :
-   "(cannot highlight method definition; try Ruby 3.5 or later)"
+   "(cannot highlight method definition; try Ruby 4.0 or later)"
    }
     END
 
@@ -1494,7 +1494,7 @@ def test_missing_keyword
       MethodDefLocationSupported ?
    "|   def keyword_test(kw1:, kw2:, kw3:)
             ^^^^^^^^^^^^" :
-   "(cannot highlight method definition; try Ruby 3.5 or later)"
+   "(cannot highlight method definition; try Ruby 4.0 or later)"
    }
     END
 
@@ -1515,7 +1515,7 @@ def test_missing_keywords # multiple missing keywords
       MethodDefLocationSupported ?
    "|   def keyword_test(kw1:, kw2:, kw3:)
             ^^^^^^^^^^^^" :
-   "(cannot highlight method definition; try Ruby 3.5 or later)"
+   "(cannot highlight method definition; try Ruby 4.0 or later)"
    }
     END
 
@@ -1536,7 +1536,7 @@ def test_unknown_keyword
       MethodDefLocationSupported ?
    "|   def keyword_test(kw1:, kw2:, kw3:)
             ^^^^^^^^^^^^" :
-   "(cannot highlight method definition; try Ruby 3.5 or later)"
+   "(cannot highlight method definition; try Ruby 4.0 or later)"
    }
     END
 
@@ -1557,7 +1557,7 @@ def test_unknown_keywords
       MethodDefLocationSupported ?
    "|   def keyword_test(kw1:, kw2:, kw3:)
             ^^^^^^^^^^^^" :
-   "(cannot highlight method definition; try Ruby 3.5 or later)"
+   "(cannot highlight method definition; try Ruby 4.0 or later)"
    }
     END
 
@@ -1587,7 +1587,7 @@ def test_wrong_number_of_arguments_for_method2
       MethodDefLocationSupported ?
    "|   def wrong_number_of_arguments_test2(
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^" :
-   "(cannot highlight method definition; try Ruby 3.5 or later)"
+   "(cannot highlight method definition; try Ruby 4.0 or later)"
    }
     END
 
@@ -1609,7 +1609,7 @@ def test_wrong_number_of_arguments_for_lambda_literal
       MethodDefLocationSupported ?
    "|     v = -> {}
               ^^" :
-   "(cannot highlight method definition; try Ruby 3.5 or later)"
+   "(cannot highlight method definition; try Ruby 4.0 or later)"
    }
     END
 
@@ -1631,7 +1631,7 @@ def test_wrong_number_of_arguments_for_lambda_method
       MethodDefLocationSupported ?
    "|     v = lambda { }
                      ^" :
-   "(cannot highlight method definition; try Ruby 3.5 or later)"
+   "(cannot highlight method definition; try Ruby 4.0 or later)"
    }
     END
 
@@ -1657,7 +1657,7 @@ def test_wrong_number_of_arguments_for_define_method
       MethodDefLocationSupported ?
    "|   define_method :define_method_test do |x, y|
                                           ^^" :
-   "(cannot highlight method definition; try Ruby 3.5 or later)"
+   "(cannot highlight method definition; try Ruby 4.0 or later)"
    }
     END