diff --git a/Adjust/sdk-core/src/main/java/com/adjust/sdk/Adjust.java b/Adjust/sdk-core/src/main/java/com/adjust/sdk/Adjust.java
index 3f39c2741..3c189ae77 100644
--- a/Adjust/sdk-core/src/main/java/com/adjust/sdk/Adjust.java
+++ b/Adjust/sdk-core/src/main/java/com/adjust/sdk/Adjust.java
@@ -15,10 +15,9 @@
  */
 public class Adjust {
     /**
-     * Singleton Adjust SDK instance.
+     * eagerly create singleton Adjust SDK instance immediately when the class is loaded or initialized by Android ClassLoader
      */
-    private static AdjustInstance defaultInstance;
-
+    private volatile AdjustInstance defaultInstance;
     /**
      * Private constructor.
      */
@@ -30,12 +29,16 @@ private Adjust() {
      *
      * @return Adjust SDK singleton instance.
      */
-    public static synchronized AdjustInstance getDefaultInstance() {
+    public static AdjustInstance getDefaultInstance() {
         @SuppressWarnings("unused")
         String VERSION = "!SDK-VERSION-STRING!:com.adjust.sdk:adjust-android:4.19.0";
 
         if (defaultInstance == null) {
-            defaultInstance = new AdjustInstance();
+            synchronized (Adjust.class) {
+                if (defaultInstance == null) {
+                    defaultInstance = new AdjustInstance();
+                }
+            }
         }
         return defaultInstance;
     }
diff --git a/CHANGELOG.md b/CHANGELOG.md
index f2d83576e..e1f866606 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,8 @@
+### Version 4.19.1 (10th December 2019)
+#### Added
+- removed locking from singleton instance creation
+
+
 ### Version 4.19.0 (9th December 2019)
 #### Added
 - Added `disableThirdPartySharing(Context)` method to `Adjust` interface to allow disabling of data sharing with third parties outside of Adjust ecosystem.
diff --git a/VERSION b/VERSION
index a69aa5a42..1fc0e81ec 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-4.19.0
+4.19.1