diff --git a/library/build.gradle.kts b/library/build.gradle.kts
index a57535c..dc2df62 100644
--- a/library/build.gradle.kts
+++ b/library/build.gradle.kts
@@ -24,7 +24,7 @@ android {
 
         externalNativeBuild {
             cmake {
-                arguments += listOf("-DANDROID_SUPPORT_FLEXIBLE_PAGE_SIZES=ON")
+                arguments += listOf("-DANDROID_SUPPORT_FLEXIBLE_PAGE_SIZES=ON", "-DCMAKE_POLICY_VERSION_MINIMUM=3.5")
                 targets("session_util")
             }
         }
@@ -40,10 +40,7 @@ android {
     buildTypes {
         release {
             isMinifyEnabled = false
-            proguardFiles(
-                getDefaultProguardFile("proguard-android-optimize.txt"),
-                "proguard-rules.pro"
-            )
+            consumerProguardFile(file("proguard-rules.pro"))
 
             externalNativeBuild {
                 cmake {
diff --git a/library/proguard-rules.pro b/library/proguard-rules.pro
index 481bb43..d790fc8 100644
--- a/library/proguard-rules.pro
+++ b/library/proguard-rules.pro
@@ -5,17 +5,7 @@
 # For more details, see
 #   http://developer.android.com/guide/developing/tools/proguard.html
 
-# If your project uses WebView with JS, uncomment the following
-# and specify the fully qualified class name to the JavaScript interface
-# class:
-#-keepclassmembers class fqcn.of.javascript.interface.for.webview {
-#   public *;
-#}
-
-# Uncomment this to preserve the line number information for
-# debugging stack traces.
-#-keepattributes SourceFile,LineNumberTable
-
-# If you keep the line number information, uncomment this to
-# hide the original source file name.
-#-renamesourcefileattribute SourceFile
\ No newline at end of file
+-keep class network.loki.messenger.libsession_util.** { *; }
+-keepnames class network.loki.messenger.libsession_util.** { *; }
+-keep class kotlin.Pair { *; }
+-keep class kotlin.Triple { *; }
\ No newline at end of file
diff --git a/library/src/main/cpp/config_base.cpp b/library/src/main/cpp/config_base.cpp
index 5c07ec4..077a1fd 100644
--- a/library/src/main/cpp/config_base.cpp
+++ b/library/src/main/cpp/config_base.cpp
@@ -4,11 +4,27 @@
 
 
 std::pair<std::string, std::vector<unsigned char>> extractHashAndData(JNIEnv *env, jobject kotlin_pair) {
-    jni_utils::JavaLocalRef<jclass> pair(env, env->GetObjectClass(kotlin_pair));
-    jfieldID first = env->GetFieldID(pair.get(), "first", "Ljava/lang/Object;");
-    jfieldID second = env->GetFieldID(pair.get(), "second", "Ljava/lang/Object;");
-    auto hash_as_jstring = jni_utils::JavaLocalRef(env, reinterpret_cast<jstring>(env->GetObjectField(kotlin_pair, first)));
-    auto data_as_jbytes = jni_utils::JavaLocalRef(env, reinterpret_cast<jbyteArray>(env->GetObjectField(kotlin_pair, second)));
+    struct KotlinPairClass : jni_utils::JavaClassInfo {
+        jmethodID get_first;
+        jmethodID get_second;
+
+        KotlinPairClass(JNIEnv *env, jobject obj)
+            : JavaClassInfo(env, obj)
+            , get_first(env->GetMethodID(java_class, "getFirst", "()Ljava/lang/Object;"))
+            , get_second(env->GetMethodID(java_class, "getSecond", "()Ljava/lang/Object;")) {}
+    };
+
+    static KotlinPairClass pair_class(env, kotlin_pair);
+
+    jni_utils::JavaLocalRef hash_as_jstring(
+            env,
+            reinterpret_cast<jstring>(env->CallObjectMethod(kotlin_pair, pair_class.get_first))
+    );
+
+    jni_utils::JavaLocalRef data_as_jbytes(
+            env,
+            reinterpret_cast<jbyteArray>(env->CallObjectMethod(kotlin_pair, pair_class.get_second))
+    );
 
     return std::make_pair(
             std::string(jni_utils::JavaStringRef(env, hash_as_jstring.get()).view()),
diff --git a/library/src/main/java/network/loki/messenger/libsession_util/util/Logger.kt b/library/src/main/java/network/loki/messenger/libsession_util/util/Logger.kt
index 60ded2d..2860864 100644
--- a/library/src/main/java/network/loki/messenger/libsession_util/util/Logger.kt
+++ b/library/src/main/java/network/loki/messenger/libsession_util/util/Logger.kt
@@ -1,8 +1,11 @@
 package network.loki.messenger.libsession_util.util
 
+import androidx.annotation.Keep
+
 typealias LogLevel = Int
 
 interface Logger {
+    @Keep
     fun log(message: String, category: String, level: LogLevel)
 
     companion object {