diff --git a/lib/index.d.ts b/lib/index.d.ts
index 175c382..1e0dafd 100644
--- a/lib/index.d.ts
+++ b/lib/index.d.ts
@@ -439,8 +439,9 @@ declare namespace MCR {
         /**
          * add V8 coverage from a dir
          * @param dir node v8 coverage dir
+         * @param remove whether to remove dir after added
          */
-        addFromDir: (dir: string) => Promise<void>;
+        addFromDir: (dir: string, remove?: boolean) => Promise<void>;
 
         /** generate report */
         generate: () => Promise<CoverageResults | undefined>;
diff --git a/lib/index.js b/lib/index.js
index fcca403..0344fae 100644
--- a/lib/index.js
+++ b/lib/index.js
@@ -122,11 +122,14 @@ class CoverageReport {
     }
 
     // add coverage from dir
-    async addFromDir(dir) {
+    async addFromDir(dir, remove) {
         const time_start = Date.now();
         const results = await readFromDir(this, dir);
         // remove dir after added
-        if (!Util.isDebug()) {
+        if (typeof remove !== 'boolean') {
+            remove = !Util.isDebug();
+        }
+        if (remove) {
             Util.rmSync(dir);
         }
         Util.logTime(`added from dir: ${dir}`, time_start);