diff --git a/theme/style.less b/theme/style.less
index 6b35e3af..8dbb1cfc 100644
--- a/theme/style.less
+++ b/theme/style.less
@@ -61,6 +61,7 @@
 
 .blocklyFlyoutBackground {
     fill: #525A67 !important;
+    fill-opacity: 0.5 !important;
 }
 
 /* Remove shadow around blockly blocks */