diff --git a/core/insertion_marker_previewer.ts b/core/insertion_marker_previewer.ts
index 8998985a2..c4038c0c6 100644
--- a/core/insertion_marker_previewer.ts
+++ b/core/insertion_marker_previewer.ts
@@ -15,15 +15,6 @@ import * as registry from './registry.js';
 import {Renderer as ZelosRenderer} from './renderers/zelos/renderer.js';
 import {ConnectionType} from './connection_type.js';
 
-/**
- * An error message to throw if the block created by createMarkerBlock_ is
- * missing any components.
- */
-const DUPLICATE_BLOCK_ERROR =
-  'The insertion marker previewer tried to create a marker but the result ' +
-  'is missing a connection. If you are using a mutator, make sure your ' +
-  'domToMutation method is properly defined.';
-
 export class InsertionMarkerPreviewer implements IConnectionPreviewer {
   private readonly workspace: WorkspaceSvg;
 
@@ -88,16 +79,6 @@ export class InsertionMarkerPreviewer implements IConnectionPreviewer {
     eventUtils.disable();
     try {
       this.hidePreview();
-      const dragged = draggedConn.getSourceBlock();
-      const marker = this.createInsertionMarker(dragged);
-      const markerConn = this.getMatchingConnection(
-        dragged,
-        marker,
-        draggedConn,
-      );
-      if (!markerConn) {
-        throw Error(DUPLICATE_BLOCK_ERROR);
-      }
 
       // TODO(7898): Instead of special casing, we should change the dragger to
       //   track the change in distance between the dragged connection and the