diff --git a/src/compile/render-dom/index.ts b/src/compile/render-dom/index.ts
index 039f901731..b080ddbc62 100644
--- a/src/compile/render-dom/index.ts
+++ b/src/compile/render-dom/index.ts
@@ -290,7 +290,9 @@ export default function dom(
 				}
 			});
 
-			customElements.define("${component.tag}", ${name});
+			if (!customElements.get(${component.tag})) {
+				customElements.define("${component.tag}", ${name});
+			}
 		`);
 	} else {
 		builder.addBlock(deindent`