diff --git a/modules/image/image.field.inc b/modules/image/image.field.inc
index 6d1867c..740dfb1 100644
--- a/modules/image/image.field.inc
+++ b/modules/image/image.field.inc
@@ -176,6 +176,10 @@ function _image_field_resolution_validate($element, &$form_state) {
         form_error($element[$dimension], t('Height and width values must be numeric.'));
         return;
       }
+      else if ((is_numeric($value)) && ($value < 0)) {
+        form_error($element[$dimension], t('Height and width values must be positive numbers.'));
+        return;
+      }
       if (intval($value) == 0) {
         form_error($element[$dimension], t('Both a height and width value must be specified in the !name field.', array('!name' => $element['#title'])));
         return;