Index: wp-includes/l10n.php
===================================================================
--- wp-includes/l10n.php	(revision 26748)
+++ wp-includes/l10n.php	(working copy)
@@ -71,8 +71,13 @@
  * @return string Translated text
  */
 function translate( $text, $domain = 'default' ) {
-	$translations = get_translations_for_domain( $domain );
-	$translations = $translations->translate( $text );
+	if ( is_textdomain_loaded( $domain ) ) {
+		$translations = get_translations_for_domain( $domain );
+		$translations = $translations->translate( $text );
+	} else {
+		$translations = $text;
+	}
+
 	/**
 	 * Filter text with its translation.
 	 *
@@ -118,8 +123,13 @@
  * @return string Translated text on success, original text on failure.
  */
 function translate_with_gettext_context( $text, $context, $domain = 'default' ) {
-	$translations = get_translations_for_domain( $domain );
-	$translations = $translations->translate( $text, $context );
+	if ( is_textdomain_loaded( $domain ) ) {
+		$translations = get_translations_for_domain( $domain );
+		$translations = $translations->translate( $text, $context );
+	} else {
+		$translations = $text;
+	}
+
 	/**
 	 * Filter text with its translation based on context information.
 	 *
@@ -295,8 +305,13 @@
  * @return string Either $single or $plural translated text.
  */
 function _n( $single, $plural, $number, $domain = 'default' ) {
-	$translations = get_translations_for_domain( $domain );
-	$translation = $translations->translate_plural( $single, $plural, $number );
+	if ( is_textdomain_loaded( $domain ) ) {
+		$translations = get_translations_for_domain( $domain );
+		$translation = $translations->translate_plural( $single, $plural, $number );
+	} else {
+		$translation = ( 1 == $number ) ? $single : $plural;
+	}
+
 	/**
 	 * Filter text with its translation when plural option is available.
 	 *
@@ -326,8 +341,13 @@
  * @return string Either $single or $plural translated text with context.
  */
 function _nx($single, $plural, $number, $context, $domain = 'default') {
-	$translations = get_translations_for_domain( $domain );
-	$translation = $translations->translate_plural( $single, $plural, $number, $context );
+	if ( is_textdomain_loaded( $domain ) ) {
+		$translations = get_translations_for_domain( $domain );
+		$translation = $translations->translate_plural( $single, $plural, $number, $context );
+	} else {
+		$translation = ( 1 == $number ) ? $single : $plural;
+	}
+
 	/**
 	 * Filter text with its translation while plural option and context are available.
 	 *