diff --git a/fs_mgr/libsnapshot/include/libsnapshot/snapshot.h b/fs_mgr/libsnapshot/include/libsnapshot/snapshot.h
index aeeb4aa..8d29e40 100644
--- a/fs_mgr/libsnapshot/include/libsnapshot/snapshot.h
+++ b/fs_mgr/libsnapshot/include/libsnapshot/snapshot.h
@@ -19,6 +19,7 @@
 #include <chrono>
 #include <map>
 #include <memory>
+#include <ostream>
 #include <string>
 #include <string_view>
 #include <vector>
@@ -84,6 +85,7 @@
     // operation via fastboot. This state can only be returned by WaitForMerge.
     Cancelled
 };
+std::ostream& operator<<(std::ostream& os, UpdateState state);
 
 class SnapshotManager final {
     using CreateLogicalPartitionParams = android::fs_mgr::CreateLogicalPartitionParams;
diff --git a/fs_mgr/libsnapshot/snapshot.cpp b/fs_mgr/libsnapshot/snapshot.cpp
index b5b3af3..0bf0365 100644
--- a/fs_mgr/libsnapshot/snapshot.cpp
+++ b/fs_mgr/libsnapshot/snapshot.cpp
@@ -1526,34 +1526,33 @@
     }
 }
 
-bool SnapshotManager::WriteUpdateState(LockedFile* file, UpdateState state) {
-    std::string contents;
+std::ostream& operator<<(std::ostream& os, UpdateState state) {
     switch (state) {
         case UpdateState::None:
-            contents = "none";
-            break;
+            return os << "none";
         case UpdateState::Initiated:
-            contents = "initiated";
-            break;
+            return os << "initiated";
         case UpdateState::Unverified:
-            contents = "unverified";
-            break;
+            return os << "unverified";
         case UpdateState::Merging:
-            contents = "merging";
-            break;
+            return os << "merging";
         case UpdateState::MergeCompleted:
-            contents = "merge-completed";
-            break;
+            return os << "merge-completed";
         case UpdateState::MergeNeedsReboot:
-            contents = "merge-needs-reboot";
-            break;
+            return os << "merge-needs-reboot";
         case UpdateState::MergeFailed:
-            contents = "merge-failed";
-            break;
+            return os << "merge-failed";
         default:
             LOG(ERROR) << "Unknown update state";
-            return false;
+            return os;
     }
+}
+
+bool SnapshotManager::WriteUpdateState(LockedFile* file, UpdateState state) {
+    std::stringstream ss;
+    ss << state;
+    std::string contents = ss.str();
+    if (contents.empty()) return false;
 
     if (!Truncate(file)) return false;
     if (!android::base::WriteStringToFd(contents, file->fd())) {