diff --git a/src/pumpit.ts b/src/pumpit.ts
index d9edf05..3899313 100644
--- a/src/pumpit.ts
+++ b/src/pumpit.ts
@@ -446,7 +446,7 @@ export class PumpIt {
     return result
   }
 
-  protected _validate(safe: boolean) {
+  protected _validate(safe = false) {
     const seen = new Set()
     const wantedBy = new Map()