diff --git a/core/includes/module.inc b/core/includes/module.inc
index dff74b6..da84e76 100644
--- a/core/includes/module.inc
+++ b/core/includes/module.inc
@@ -818,7 +818,7 @@ function module_invoke_all($hook) {
     if (function_exists($function)) {
       $result = call_user_func_array($function, $args);
       if (isset($result) && is_array($result)) {
-        $return = array_merge_recursive($return, $result);
+        $return = drupal_array_merge_deep($return, $result);
       }
       elseif (isset($result)) {
         $return[] = $result;
diff --git a/core/modules/rdf/rdf.module b/core/modules/rdf/rdf.module
index b2a8457..92363a1 100644
--- a/core/modules/rdf/rdf.module
+++ b/core/modules/rdf/rdf.module
@@ -95,23 +95,22 @@ function rdf_rdf_namespaces() {
  * hook_rdf_namespaces().
  */
 function rdf_get_namespaces() {
-  $rdf_namespaces = module_invoke_all('rdf_namespaces');
-  // module_invoke_all() uses array_merge_recursive() which might return nested
-  // arrays if several modules redefine the same prefix multiple times. We need
-  // to ensure the array of namespaces is flat and only contains strings as
-  // URIs.
-  foreach ($rdf_namespaces as $prefix => $uri) {
-    if (is_array($uri)) {
-      if (count(array_unique($uri)) == 1) {
-        // All namespaces declared for this prefix are the same, merge them all
-        // into a single namespace.
-        $rdf_namespaces[$prefix] = $uri[0];
-      }
-      else {
-        // There are conflicting namespaces for this prefix, do not include
-        // duplicates in order to avoid asserting any inaccurate RDF
-        // statements.
-        unset($rdf_namespaces[$prefix]);
+  // Do the equivalent of module_invoke_all('rdf_namespaces'), but exclude
+  // prefixes for which different modules define conflicting URIs.
+  $rdf_namespaces = array();
+  $conflicts = array();
+  foreach (module_implements('rdf_namespaces') as $module) {
+    $function = $module . '_rdf_namespaces';
+    $result = $function();
+    if (is_array($result)) {
+      foreach ($result as $prefix => $uri) {
+        if (isset($rdf_namespaces[$prefix]) && $rdf_namespaces[$prefix] !== $uri) {
+          $conflicts[$prefix] = TRUE;
+          unset($rdf_namespaces[$prefix]);
+        }
+        if (!isset($conflicts[$prefix])) {
+          $rdf_namespaces[$prefix] = $uri;
+        }
       }
     }
   }
@@ -672,7 +671,7 @@ function rdf_preprocess_username(&$variables) {
   // (see http://www.w3.org/TR/rdfa-syntax/#rdfa-attributes).
   // Therefore, merge rather than override so as not to clobber values set by
   // earlier preprocess functions.
-  $variables['attributes_array'] = array_merge_recursive($variables['attributes_array'], $attributes);
+  $variables['attributes_array'] = drupal_array_merge_deep($variables['attributes_array'], $attributes);
 }
 
 /**