diff --git a/src/vs/platform/contextkey/common/contextkey.ts b/src/vs/platform/contextkey/common/contextkey.ts
index f40bd669a54637917d4d066f674dba31795cd86f..208cfa184bfdf3d36679a50291bf608183c3531d 100644
--- a/src/vs/platform/contextkey/common/contextkey.ts
+++ b/src/vs/platform/contextkey/common/contextkey.ts
@@ -400,7 +400,7 @@ export class ContextKeyRegexExpr implements ContextKeyExpr {
 	}
 
 	public serialize(): string {
-		return `${this.keys} =~ /${this.regexp ? this.regexp.source : '<invalid>'}/`;
+		return `${this.key} =~ /${this.regexp ? this.regexp.source : '<invalid>'}/`;
 	}
 
 	public keys(): string[] {