diff --git a/cmds/idmap2/idmap2d/Idmap2Service.cpp b/cmds/idmap2/idmap2d/Idmap2Service.cpp
index cf72cb9..86b00f1 100644
--- a/cmds/idmap2/idmap2d/Idmap2Service.cpp
+++ b/cmds/idmap2/idmap2d/Idmap2Service.cpp
@@ -78,6 +78,18 @@
   }
 }
 
+Status Idmap2Service::verifyIdmap(const std::string& overlay_apk_path,
+                                  int32_t user_id ATTRIBUTE_UNUSED, bool* _aidl_return) {
+  assert(_aidl_return);
+  const std::string idmap_path = Idmap::CanonicalIdmapPathFor(kIdmapCacheDir, overlay_apk_path);
+  std::ifstream fin(idmap_path);
+  const std::unique_ptr<const IdmapHeader> header = IdmapHeader::FromBinaryStream(fin);
+  fin.close();
+  std::stringstream dev_null;
+  *_aidl_return = header && header->IsUpToDate(dev_null);
+  return ok();
+}
+
 Status Idmap2Service::createIdmap(const std::string& target_apk_path,
                                   const std::string& overlay_apk_path, int32_t user_id,
                                   std::unique_ptr<std::string>* _aidl_return) {
@@ -90,17 +102,6 @@
 
   _aidl_return->reset(nullptr);
 
-  const std::string idmap_path = Idmap::CanonicalIdmapPathFor(kIdmapCacheDir, overlay_apk_path);
-  std::ifstream fin(idmap_path);
-  const std::unique_ptr<const IdmapHeader> header = IdmapHeader::FromBinaryStream(fin);
-  fin.close();
-  // do not reuse error stream from IsUpToDate below, or error messages will be
-  // polluted with irrelevant data
-  std::stringstream dev_null;
-  if (header && header->IsUpToDate(dev_null)) {
-    return ok();
-  }
-
   const std::unique_ptr<const ApkAssets> target_apk = ApkAssets::Load(target_apk_path);
   if (!target_apk) {
     return error("failed to load apk " + target_apk_path);
@@ -119,6 +120,7 @@
   }
 
   umask(0133);  // u=rw,g=r,o=r
+  const std::string idmap_path = Idmap::CanonicalIdmapPathFor(kIdmapCacheDir, overlay_apk_path);
   std::ofstream fout(idmap_path);
   if (fout.fail()) {
     return error("failed to open idmap path " + idmap_path);
diff --git a/cmds/idmap2/idmap2d/Idmap2Service.h b/cmds/idmap2/idmap2d/Idmap2Service.h
index 2b32042..4e5abc9 100644
--- a/cmds/idmap2/idmap2d/Idmap2Service.h
+++ b/cmds/idmap2/idmap2d/Idmap2Service.h
@@ -39,6 +39,9 @@
   binder::Status removeIdmap(const std::string& overlay_apk_path, int32_t user_id,
                              bool* _aidl_return);
 
+  binder::Status verifyIdmap(const std::string& overlay_apk_path, int32_t user_id,
+                             bool* _aidl_return);
+
   binder::Status createIdmap(const std::string& target_apk_path,
                              const std::string& overlay_apk_path, int32_t user_id,
                              std::unique_ptr<std::string>* _aidl_return);
diff --git a/cmds/idmap2/idmap2d/aidl/android/os/IIdmap2.aidl b/cmds/idmap2/idmap2d/aidl/android/os/IIdmap2.aidl
index 5d19610..d475417 100644
--- a/cmds/idmap2/idmap2d/aidl/android/os/IIdmap2.aidl
+++ b/cmds/idmap2/idmap2d/aidl/android/os/IIdmap2.aidl
@@ -22,6 +22,7 @@
 interface IIdmap2 {
   @utf8InCpp String getIdmapPath(@utf8InCpp String overlayApkPath, int userId);
   boolean removeIdmap(@utf8InCpp String overlayApkPath, int userId);
+  boolean verifyIdmap(@utf8InCpp String overlayApkPath, int userId);
   @nullable @utf8InCpp String createIdmap(@utf8InCpp String targetApkPath,
                                           @utf8InCpp String overlayApkPath, int userId);
 }