diff --git a/coreapi/linphonecore_jni.cc b/coreapi/linphonecore_jni.cc
index eb7c47f83..e9fc0b787 100644
--- a/coreapi/linphonecore_jni.cc
+++ b/coreapi/linphonecore_jni.cc
@@ -1160,10 +1160,23 @@ extern "C" jlong Java_org_linphone_core_LinphoneCoreImpl_newLinphoneCore(JNIEnv*
 	if (factoryConfig) env->ReleaseStringUTFChars(jfactoryConfig, factoryConfig);
 	return nativePtr;
 }
-extern "C" void Java_org_linphone_core_LinphoneCoreImpl_delete(JNIEnv* env, jobject thiz, jlong lc) {
-	jobject core = (jobject)linphone_core_get_user_data((LinphoneCore*)lc);
-	linphone_core_destroy((LinphoneCore*)lc);
+extern "C" void Java_org_linphone_core_LinphoneCoreImpl_delete(JNIEnv* env, jobject thiz, jlong native_ptr) {
+	LinphoneCore *lc=(LinphoneCore*)native_ptr;
+	jobject core = (jobject)linphone_core_get_user_data(lc);
+
+	jobject multicast_lock = lc->multicast_lock;
+	jobject multicast_lock_class = lc->multicast_lock_class;
+	jobject wifi_lock = lc->wifi_lock;
+	jobject wifi_lock_class = lc->wifi_lock_class;
+
+	linphone_core_destroy(lc);
 	ms_exit();
+
+	if (wifi_lock) env->DeleteGlobalRef(wifi_lock);
+	if (wifi_lock_class) env->DeleteGlobalRef(wifi_lock_class);
+	if (multicast_lock) env->DeleteGlobalRef(multicast_lock);
+	if (multicast_lock_class) env->DeleteGlobalRef(multicast_lock_class);
+
 	if (core) {
 		env->DeleteGlobalRef(core);
 	}
@@ -4082,33 +4095,43 @@ extern "C" void Java_org_linphone_core_LinphoneCoreImpl_setAndroidPowerManager(J
 #endif
 }
 
+/*released in Java_org_linphone_core_LinphoneCoreImpl_delete*/
 extern "C" void Java_org_linphone_core_LinphoneCoreImpl_setAndroidWifiLock(JNIEnv *env, jobject thiz, jlong ptr, jobject wifi_lock) {
 #ifdef ANDROID
 	LinphoneCore *lc=(LinphoneCore*)ptr;
-	if (lc->wifi_lock)
+	if (lc->wifi_lock) {
 		env->DeleteGlobalRef(lc->wifi_lock);
+		env->DeleteGlobalRef(lc->wifi_lock_class);
+	}
 	if (wifi_lock != NULL) {
 		lc->wifi_lock=env->NewGlobalRef(wifi_lock);
-		jclass wifiLockClass = env->FindClass("android/net/wifi/WifiManager$WifiLock");
-		lc->wifi_lock_acquire_id = env->GetMethodID(wifiLockClass, "acquire", "()V");
-		lc->wifi_lock_release_id = env->GetMethodID(wifiLockClass, "release", "()V");
+		lc->wifi_lock_class = env->FindClass("android/net/wifi/WifiManager$WifiLock");
+		lc->wifi_lock_class = (jclass)env->NewGlobalRef(lc->wifi_lock_class); /*to make sure methodid are preserved*/
+		lc->wifi_lock_acquire_id = env->GetMethodID(lc->wifi_lock_class, "acquire", "()V");
+		lc->wifi_lock_release_id = env->GetMethodID(lc->wifi_lock_class, "release", "()V");
 	} else {
 		lc->wifi_lock=NULL;
+		lc->wifi_lock_class=NULL;
 	}
 #endif
 }
+/*released in Java_org_linphone_core_LinphoneCoreImpl_delete*/
 extern "C" void Java_org_linphone_core_LinphoneCoreImpl_setAndroidMulticastLock(JNIEnv *env, jobject thiz, jlong ptr, jobject multicast_lock) {
 #ifdef ANDROID
 	LinphoneCore *lc=(LinphoneCore*)ptr;
-	if (lc->multicast_lock)
+	if (lc->multicast_lock) {
 		env->DeleteGlobalRef(lc->multicast_lock);
+		env->DeleteGlobalRef(lc->multicast_lock_class);
+	}
 	if (multicast_lock != NULL) {
 		lc->multicast_lock=env->NewGlobalRef(multicast_lock);
-		jclass multicastLockClass = env->FindClass("android/net/wifi/WifiManager$MulticastLock");
-		lc->multicast_lock_acquire_id = env->GetMethodID(multicastLockClass, "acquire", "()V");
-		lc->multicast_lock_release_id = env->GetMethodID(multicastLockClass, "release", "()V");
+		lc->multicast_lock_class = env->FindClass("android/net/wifi/WifiManager$MulticastLock");
+		lc->multicast_lock_class = (jclass)env->NewGlobalRef(lc->multicast_lock_class);/*to make sure methodid are preserved*/
+		lc->multicast_lock_acquire_id = env->GetMethodID(lc->multicast_lock_class, "acquire", "()V");
+		lc->multicast_lock_release_id = env->GetMethodID(lc->multicast_lock_class, "release", "()V");
 	} else {
 		lc->multicast_lock=NULL;
+		lc->multicast_lock_class=NULL;
 	}
 #endif
 }
diff --git a/coreapi/private.h b/coreapi/private.h
index d5a59d85f..4414f50ec 100644
--- a/coreapi/private.h
+++ b/coreapi/private.h
@@ -805,9 +805,11 @@ struct _LinphoneCore
 	LinphoneCoreVTable *current_vtable; // the latest vtable to call a callback, see linphone_core_get_current_vtable
 #ifdef ANDROID
 	jobject wifi_lock;
+	jclass wifi_lock_class;
 	jmethodID wifi_lock_acquire_id;
 	jmethodID wifi_lock_release_id;
 	jobject multicast_lock;
+	jclass multicast_lock_class;
 	jmethodID multicast_lock_acquire_id;
 	jmethodID multicast_lock_release_id;
 #endif
diff --git a/mediastreamer2 b/mediastreamer2
index ed0c1f307..ca8ad4af2 160000
--- a/mediastreamer2
+++ b/mediastreamer2
@@ -1 +1 @@
-Subproject commit ed0c1f30701c6a3bb0607243834f5b58a2720381
+Subproject commit ca8ad4af235b8131d43687343577e98ba0142c72