diff --git a/benchmark/index.mjs b/benchmark/index.mjs
index 1898a7a..df606ff 100644
--- a/benchmark/index.mjs
+++ b/benchmark/index.mjs
@@ -75,6 +75,13 @@ async function bench() {
 	}, s => {
 		s.replace(/replacement/g, 'replacement\nReplacement');
 	});
+
+	const size = 1000000;
+	runWithInstance('overwrite', ['a'.repeat(size)], s => {
+		for (let i = 1; i < size; i+=2) {
+			s.overwrite(i, i+1, 'b');
+		}
+	});
 }
 
 bench();
diff --git a/src/Chunk.js b/src/Chunk.js
index 53ce9a5..e15cc6a 100644
--- a/src/Chunk.js
+++ b/src/Chunk.js
@@ -11,11 +11,16 @@ export default class Chunk {
 		this.storeName = false;
 		this.edited = false;
 
-		// we make these non-enumerable, for sanity while debugging
-		Object.defineProperties(this, {
-			previous: { writable: true, value: null },
-			next: { writable: true, value: null },
-		});
+		if (DEBUG) {
+			// we make these non-enumerable, for sanity while debugging
+			Object.defineProperties(this, {
+				previous: { writable: true, value: null },
+				next: { writable: true, value: null },
+			});
+		} else {
+			this.previous = null;
+			this.next = null;
+		}
 	}
 
 	appendLeft(content) {