diff --git a/resources/gen-changelog.ts b/resources/gen-changelog.ts
index 15192bb4ed..46124c8198 100644
--- a/resources/gen-changelog.ts
+++ b/resources/gen-changelog.ts
@@ -88,7 +88,7 @@ async function genChangeLog(): Promise<string> {
     }
 
     const label = labels[0];
-    if (labelsConfig[label] != null) {
+    if (labelsConfig[label] == null) {
       throw new Error(`Unknown label: ${label}. See ${pr.url}`);
     }
     byLabel[label] ??= [];