diff --git a/includes/locale.inc b/includes/locale.inc
index 0db4d4a..72e4668 100644
--- a/includes/locale.inc
+++ b/includes/locale.inc
@@ -978,7 +978,7 @@ function _locale_import_one_string($op, $value = NULL, $mode = NULL, $lang = NUL
           // data untouched or if we don't have an existing plural formula.
           $header = _locale_import_parse_header($value['msgstr']);
 
-          // Get the plural formula and update in database.
+          // Get and store the plural formula if available.
           if (isset($header["Plural-Forms"]) && $p = _locale_import_parse_plural_forms($header["Plural-Forms"], $file->uri)) {
             list($nplurals, $plural) = $p;
             db_update('languages')
@@ -989,15 +989,6 @@ function _locale_import_one_string($op, $value = NULL, $mode = NULL, $lang = NUL
               ->condition('language', $lang)
               ->execute();
           }
-          else {
-            db_update('languages')
-              ->fields(array(
-                'plurals' => 0,
-                'formula' => '',
-              ))
-              ->condition('language', $lang)
-              ->execute();
-          }
         }
         $header_done = TRUE;
       }
diff --git a/modules/locale/locale.test b/modules/locale/locale.test
index db0bead..fdafd72 100644
--- a/modules/locale/locale.test
+++ b/modules/locale/locale.test
@@ -793,6 +793,23 @@ class LocaleImportFunctionalTest extends DrupalWebTestCase {
     // This import should not have changed number of plural forms.
     $this->assert(db_query("SELECT plurals FROM {languages} WHERE language = 'fr'")->fetchField() == 2, t('Plural numbers untouched.'));
 
+    $this->importPoFile($this->getPoFileWithBrokenPlural(), array(
+      'langcode' => 'fr',
+      'mode' => 1, // Existing strings are kept, only new strings are added.
+    ));
+
+    // Attempt to import broken .po file as well to prove that this
+    // will not overwrite the proper plural formula imported above.
+    $this->assert(db_query("SELECT plurals FROM {languages} WHERE language = 'fr'")->fetchField() == 2, t('Broken plurals: plural numbers untouched.'));
+
+    $this->importPoFile($this->getPoFileWithMissingPlural(), array(
+      'langcode' => 'fr',
+      'mode' => 1, // Existing strings are kept, only new strings are added.
+    ));
+
+    // Attempt to import .po file which has no plurals and prove that this
+    // will not overwrite the proper plural formula imported above.
+    $this->assert(db_query("SELECT plurals FROM {languages} WHERE language = 'fr'")->fetchField() == 2, t('No plurals: plural numbers untouched.'));
+
+
     // Try importing a .po file with overriding strings, and ensure existing
     // strings are overwritten.
     $this->importPoFile($this->getOverwritePoFile(), array(
@@ -1072,6 +1089,42 @@ msgstr ""
 EOF;
   }
 
+
+  /**
+   * Returns a .po file with a missing plural formula.
+   */
+  function getPoFileWithMissingPlural() {
+    return <<< EOF
+msgid ""
+msgstr ""
+"Project-Id-Version: Drupal 7\\n"
+"MIME-Version: 1.0\\n"
+"Content-Type: text/plain; charset=UTF-8\\n"
+"Content-Transfer-Encoding: 8bit\\n"
+
+msgid "Monday"
+msgstr "Ponedjeljak"
+EOF;
+  }
+
+  /**
+   * Returns a .po file with a broken plural formula.
+   */
+  function getPoFileWithBrokenPlural() {
+    return <<< EOF
+msgid ""
+msgstr ""
+"Project-Id-Version: Drupal 7\\n"
+"MIME-Version: 1.0\\n"
+"Content-Type: text/plain; charset=UTF-8\\n"
+"Content-Transfer-Encoding: 8bit\\n"
+"Plural-Forms: broken, will not parse\\n"
+
+msgid "Monday"
+msgstr "lundi"
+EOF;
+  }
+
 }
 
 /**