diff -u b/core/modules/rdf/rdf.module b/core/modules/rdf/rdf.module
--- b/core/modules/rdf/rdf.module
+++ b/core/modules/rdf/rdf.module
@@ -418,6 +418,15 @@
   if (!empty($variables['homepage']) && !empty($homepage_mapping)) {
     $attributes['rel'] = $homepage_mapping['properties'];
   }
+  // Long usernames are truncated by template_preprocess_username().
+  // In these cases, store the full username in the 'content' attribute.
+  if ($variables['truncated']) {
+    $attributes['content'] = check_plain($variables['name_raw']);
+    // If we don't unset the 'datatype' attribute, EasyRdf_Parser_Rdfa will
+    // ignore the 'content' attribute and still use the element's text content
+    // (that is, the shortened username).
+    unset($attributes['datatype']);
+  }
   // The remaining attributes can have multiple values listed, with whitespace
   // separating the values in the RDFa attributes
   // (see http://www.w3.org/TR/rdfa-syntax/#rdfa-attributes).
@@ -434,16 +443,6 @@
   if (!empty($variables['homepage']) && !empty($homepage_mapping)) {
     $attributes['rel'] = $homepage_mapping['properties'];
   }
-  // Usernames over 20 characters in length are truncated
-  // by template_preprocess_username().
-  // In these cases, store the full username in the 'content' attribute.
-  if (drupal_strlen($variables['name_raw']) > 20) {
-    $attributes['content'] = check_plain($variables['name_raw']);
-    // If we don't unset the 'datatype' attribute, EasyRdf_Parser_Rdfa will
-    // ignore the 'content' attribute and still use the element's text content
-    // (that is, the shortened username).
-    unset($attributes['datatype']);
-  }
   // The remaining attributes can have multiple values listed, with whitespace
   // separating the values in the RDFa attributes
   // (see http://www.w3.org/TR/rdfa-syntax/#rdfa-attributes).
only in patch2:
unchanged:
--- a/core/modules/user/user.module
+++ b/core/modules/user/user.module
@@ -635,6 +635,10 @@ function template_preprocess_username(&$variables) {
   $name = $variables['name_raw'] = $account->getUsername();
   if (drupal_strlen($name) > 20) {
     $name = drupal_substr($name, 0, 15) . '...';
+    $variables['truncated'] = TRUE;
+  }
+  else {
+    $variables['truncated'] = FALSE;
   }
   $variables['name'] = check_plain($name);
   $variables['profile_access'] = user_access('access user profiles');