diff --git a/src/vs/base/common/map.ts b/src/vs/base/common/map.ts
index e9b7a4c065ff2f..6f79e1e81402b0 100644
--- a/src/vs/base/common/map.ts
+++ b/src/vs/base/common/map.ts
@@ -770,6 +770,9 @@ export class BidirectionalMap<K, V> {
 	}
 
 	set(key: K, value: V): void {
+		if (this._m1.has(key)) {
+			this._m2.delete(this._m1.get(key)!);
+		}
 		this._m1.set(key, value);
 		this._m2.set(value, key);
 	}
diff --git a/src/vs/base/test/common/map.test.ts b/src/vs/base/test/common/map.test.ts
index dd7c4a1841a049..e5af65b3e982a2 100644
--- a/src/vs/base/test/common/map.test.ts
+++ b/src/vs/base/test/common/map.test.ts
@@ -609,6 +609,16 @@ suite('BidirectionalMap', () => {
 		assert.strictEqual(map.delete('four'), false);
 	});
 
+	test('should not leave a stale reverse entry when a key value is updated', () => {
+		const map = new BidirectionalMap<string, number>();
+		map.set('one', 1);
+		map.set('one', 2);
+
+		assert.strictEqual(map.get('one'), 2);
+		assert.strictEqual(map.getKey(2), 'one');
+		assert.strictEqual(map.getKey(1), undefined);
+	});
+
 	test('should handle forEach correctly', () => {
 		const map = new BidirectionalMap<string, number>();
 		map.set('one', 1);