diff --git a/app/javascript/mastodon/features/compose/components/compose_form.js b/app/javascript/mastodon/features/compose/components/compose_form.js
index 9fc5f395c..5c916261e 100644
--- a/app/javascript/mastodon/features/compose/components/compose_form.js
+++ b/app/javascript/mastodon/features/compose/components/compose_form.js
@@ -90,7 +90,7 @@ class ComposeForm extends ImmutablePureComponent {
     const fulltext = this.getFulltextForCharacterCounting();
     const isOnlyWhitespace = fulltext.length !== 0 && fulltext.trim().length === 0;
 
-    return !(isSubmitting || isUploading || isChangingUpload || length(fulltext) > 500 || (isOnlyWhitespace && !anyMedia));
+    return !(isSubmitting || isUploading || isChangingUpload || length(fulltext) > 640 || (isOnlyWhitespace && !anyMedia));
   }
 
   handleSubmit = (e) => {
@@ -277,7 +277,7 @@ class ComposeForm extends ImmutablePureComponent {
           </div>
 
           <div className='character-counter__wrapper'>
-            <CharacterCounter max={500} text={this.getFulltextForCharacterCounting()} />
+            <CharacterCounter max={640} text={this.getFulltextForCharacterCounting()} />
           </div>
         </div>
 
diff --git a/app/validators/status_length_validator.rb b/app/validators/status_length_validator.rb
index e107912b7..0e7412070 100644
--- a/app/validators/status_length_validator.rb
+++ b/app/validators/status_length_validator.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 class StatusLengthValidator < ActiveModel::Validator
-  MAX_CHARS = 500
+  MAX_CHARS = 640
   URL_PLACEHOLDER_CHARS = 23
   URL_PLACEHOLDER = 'x' * 23