diff --git a/includes/commerce_fedex.admin.inc b/includes/commerce_fedex.admin.inc
index ed7f005..3286250 100644
--- a/includes/commerce_fedex.admin.inc
+++ b/includes/commerce_fedex.admin.inc
@@ -227,14 +227,14 @@ function commerce_fedex_settings_form_validate($form, $form_state) {
   // Define numeric fields that should be validated.
   $numeric_fields = array(
     'commerce_fedex_default_package_size_length' => t('length'),
-    'commerce_fedex_default_package_size_width' => t('height'),
-    'commerce_fedex_default_package_size_height' => t('width'),
+    'commerce_fedex_default_package_size_width' => t('width'),
+    'commerce_fedex_default_package_size_height' => t('height'),
   );
 
   // Validate any numeric fields within the submitted values.
   foreach ($numeric_fields as $key => $numeric_field) {
-    if (!is_numeric($form_state['values'][$key])) {
-      form_set_error($numeric_field, t('Values for @field can only be set to positive numeric values.', array('@field' => $numeric_field)));
+    if (!empty($form_state['values'][$key]) && !is_numeric($form_state['values'][$key])) {
+      form_set_error($key, t('Values for @field can only be set to positive numeric values.', array('@field' => $numeric_field)));
     }
   }