diff -u b/core/includes/gettext.inc b/core/includes/gettext.inc
--- b/core/includes/gettext.inc
+++ b/core/includes/gettext.inc
@@ -408,7 +408,7 @@
         // If 'msgid' is empty, it means we got values for the header of the
         // file as per the structure of the Gettext format.
         $locale_plurals = variable_get('locale_translation_plurals', array());
-        if (count(array_filter($overwrite_options)) || empty($locale_plurals[$lang]['plurals'])) {
+        if (array_sum($overwrite_options) || empty($locale_plurals[$lang]['plurals'])) {
           // Since we only need to parse the header if we ought to update the
           // plural formula, only run this if we don't need to keep existing
           // data untouched or if we don't have an existing plural formula.
@@ -488,33 +488,34 @@
   );
 
   // Look up the source string and any existing translation.
-  $existing_translation = NULL;
-  $lid = db_query("SELECT lid FROM {locales_source} WHERE source = :source AND context = :context", array(':source' => $source, ':context' => $context))->fetchField();
-  if ($lid) {
-    $existing_translation = db_query("SELECT * FROM {locales_target} WHERE lid = :lid AND language = :language", array(':lid' => $lid, ':language' => $langcode))->fetchObject();
-  }
+  $string = db_query("SELECT s.lid, t.customized FROM {locales_source} s LEFT JOIN {locales_target} t ON s.lid = t.lid AND t.language = :language WHERE s.source = :source AND s.context = :context", array(
+    ':source' => $source,
+    ':context' => $context,
+    ':language' => $langcode,
+    ))
+    ->fetchObject();
 
   if (!empty($translation)) {
     // Skip this string unless it passes a check for dangerous code.
     if (!locale_string_is_safe($translation)) {
       watchdog('locale', 'Import of string "%string" was skipped because of disallowed or malformed HTML.', array('%string' => $translation), WATCHDOG_ERROR);
       $report['skips']++;
-      $lid = 0;
+      return 0;
     }
-    elseif ($lid) {
+    elseif (isset($string->lid)) {
       // We have this source string saved already.
       db_update('locales_source')
         ->fields(array(
           'location' => $location,
         ))
-        ->condition('lid', $lid)
+        ->condition('lid', $string->lid)
         ->execute();
 
-      if (empty($existing_translation)) {
+      if (!isset($string->customized)) {
         // No translation in this language.
         db_insert('locales_target')
           ->fields(array(
-            'lid' => $lid,
+            'lid' => $string->lid,
             'language' => $langcode,
             'translation' => $translation,
             'customized' => $customized,
@@ -523,7 +524,7 @@
 
         $report['additions']++;
       }
-      elseif ($overwrite_options[$existing_translation->customized ? 'customized' : 'not_customized']) {
+      elseif ($overwrite_options[$string->customized ? 'customized' : 'not_customized']) {
         // Translation exists, only overwrite if instructed.
         db_update('locales_target')
           ->fields(array(
@@ -531,11 +532,12 @@
             'customized' => $customized,
           ))
           ->condition('language', $langcode)
-          ->condition('lid', $lid)
+          ->condition('lid', $string->lid)
           ->execute();
 
         $report['updates']++;
       }
+      return $string->lid;
     }
     else {
       // No such source string in the database yet.
@@ -557,19 +559,19 @@
         ->execute();
 
       $report['additions']++;
+      return $lid;
     }
   }
-  elseif (!empty($existing_translation) && $overwrite_options[$existing_translation->customized ? 'customized' : 'not_customized']) {
+  elseif (isset($string->lid) && isset($string->customized) && $overwrite_options[$string->customized ? 'customized' : 'not_customized']) {
     // Empty translation, remove existing if instructed.
     db_delete('locales_target')
       ->condition('language', $langcode)
-      ->condition('lid', $lid)
+      ->condition('lid', $string->lid)
       ->execute();
 
     $report['deletes']++;
+    return $string->lid;
   }
-
-  return $lid;
 }
 
 /**
diff -u b/core/modules/locale/locale.test b/core/modules/locale/locale.test
--- b/core/modules/locale/locale.test
+++ b/core/modules/locale/locale.test
@@ -1485,7 +1485,7 @@
     return <<< EOF
 msgid ""
 msgstr ""
-"Project-Id-Version: Drupal 6\\n"
+"Project-Id-Version: Drupal 8\\n"
 "MIME-Version: 1.0\\n"
 "Content-Type: text/plain; charset=UTF-8\\n"
 "Content-Transfer-Encoding: 8bit\\n"
@@ -1504,7 +1504,7 @@
     return <<< EOF
 msgid ""
 msgstr ""
-"Project-Id-Version: Drupal 6\\n"
+"Project-Id-Version: Drupal 8\\n"
 "MIME-Version: 1.0\\n"
 "Content-Type: text/plain; charset=UTF-8\\n"
 "Content-Transfer-Encoding: 8bit\\n"