diff --git a/assets/css/src/newsletter_editor/contentBlocks/base.styl b/assets/css/src/newsletter_editor/contentBlocks/base.styl
index 8addde47df..0d1684ff99 100644
--- a/assets/css/src/newsletter_editor/contentBlocks/base.styl
+++ b/assets/css/src/newsletter_editor/contentBlocks/base.styl
@@ -21,6 +21,8 @@ $block-text-line-height = $text-line-height
     left: 0
     pointer-events: none
     border: 1px solid $transparent-color
+    -webkit-transition: 0.3s;
+    transition: 0.3s;
 
   &:hover > .mailpoet_block_highlight
     border: 1px dashed $block-hover-highlight-color