diff --git a/app/assets/javascripts/components/box_batches_form.js.jsx b/app/assets/javascripts/components/box_batches_form.js.jsx
index c7ed38dec..3795f00d1 100644
--- a/app/assets/javascripts/components/box_batches_form.js.jsx
+++ b/app/assets/javascripts/components/box_batches_form.js.jsx
@@ -301,7 +301,7 @@ var BoxBatchForm = React.createClass({
   },
 
   isValidConcentration: function (c) {
-    return (parseInt(c.replicate, 10) > 0 && parseFloat(c.concentration, 10) > 0);
+    return (parseInt(c.replicate, 10) > 0 && parseFloat(c.concentration, 10) >= 0);
   },
 
   hideForm: function (event) {
diff --git a/app/assets/stylesheets/_batches.scss b/app/assets/stylesheets/_batches.scss
index f63ade217..79d0dd5eb 100644
--- a/app/assets/stylesheets/_batches.scss
+++ b/app/assets/stylesheets/_batches.scss
@@ -170,13 +170,9 @@
   display: flex;
   align-items: center;
   margin-left: auto;
-  
-  .icon-check {
-    width: 24px;
-    height: 24px;
-    margin-left: 10px;
-    background-size: 100%;
-    cursor: pointer;
+
+  >input{
+    width: 80px;
   }
 }
 
diff --git a/spec/features/boxes_spec.rb b/spec/features/boxes_spec.rb
index 61573d9b5..9b09c9e5c 100644
--- a/spec/features/boxes_spec.rb
+++ b/spec/features/boxes_spec.rb
@@ -64,9 +64,12 @@
 
           # validates concentration field:
           field = batch_form.concentration_fields[0]
-          field.set(0)
+          field.set(-1)
           expect(batch_form.ok.disabled?).to be(true)
 
+          field.set(0)
+          expect(batch_form.ok.disabled?).to be(false)
+
           field.set(2)
           expect(batch_form.ok.disabled?).to be(false)
         end