diff --git a/question/type/numerical/questiontype.php b/question/type/numerical/questiontype.php
index a4526b1b1a4..4a490061d51 100644
--- a/question/type/numerical/questiontype.php
+++ b/question/type/numerical/questiontype.php
@@ -428,7 +428,7 @@ class question_numerical_qtype extends question_shortanswer_qtype {
         // before i.e. at left or after at rigth of the unit variants.
         $nameunit   = "name=\"".$question->name_prefix."unit\"";
         $nameanswer   = "name=\"".$question->name_prefix."answer\"";
-        if (isset($state->responses['']) && $state->responses[''] != ''){
+        if (isset($state->responses['']) && $state->responses[''] != '' && !isset($state->responses['answer'])){
               $this->split_old_answer($state->responses[''], $question->options->units, $state->responses['answer'] ,$state->responses['unit'] );
         }
         if (isset($state->responses['answer']) && $state->responses['answer']!='') {