diff --git a/sdk/src/main/java/com/deploygate/sdk/SdkDeviceStatesCollector.java b/sdk/src/main/java/com/deploygate/sdk/SdkDeviceStatesCollector.java
index b2657f8..b6ff69a 100644
--- a/sdk/src/main/java/com/deploygate/sdk/SdkDeviceStatesCollector.java
+++ b/sdk/src/main/java/com/deploygate/sdk/SdkDeviceStatesCollector.java
@@ -11,10 +11,18 @@
 
 final class SdkDeviceStatesCollector {
 
-    private final JSONObject states = new JSONObject();
+    private final Object mLock;
+    private final JSONObject states;
+
+    SdkDeviceStatesCollector() {
+        mLock = new Object();
+        states = new JSONObject();
+    }
 
     public String getJSONString() {
-        return states.toString();
+        synchronized (mLock) {
+            return states.toString();
+        }
     }
 
     public void collectLocale() {
@@ -43,8 +51,11 @@ public void collectLocale() {
 
     private void putState(String fqcn, String paramName, Object data) {
         String key = String.format("%s$%s", fqcn, paramName);
+
         try {
-            states.put(key, data);
+            synchronized (mLock) {
+                states.put(key, data);
+            }
         } catch (JSONException e) {
             Logger.w(e, "Failed to put info: key=%s, value=%s", key, data);
         }