diff --git a/coreapi/linphonecore_jni.cc b/coreapi/linphonecore_jni.cc
index cf2a99c06..e0a7f3e7e 100644
--- a/coreapi/linphonecore_jni.cc
+++ b/coreapi/linphonecore_jni.cc
@@ -298,8 +298,8 @@ extern "C" jlong Java_org_linphone_core_LinphoneCoreImpl_newLinphoneCore(JNIEnv*
 		,jstring jfactoryConfig
 		,jobject  juserdata){
 
-	const char* userConfig = env->GetStringUTFChars(juserConfig, NULL);
-	const char* factoryConfig = env->GetStringUTFChars(jfactoryConfig, NULL);
+	const char* userConfig = juserConfig?env->GetStringUTFChars(juserConfig, NULL):NULL;
+	const char* factoryConfig = jfactoryConfig?env->GetStringUTFChars(jfactoryConfig, NULL):NULL;
 	LinphoneCoreData* ldata = new LinphoneCoreData(env,thiz,jlistener,juserdata);
 #ifdef ANDROID
 	ms_andsnd_set_jvm(jvm);
@@ -317,8 +317,8 @@ extern "C" jlong Java_org_linphone_core_LinphoneCoreImpl_newLinphoneCore(JNIEnv*
 	//clear existing proxy config
 	linphone_core_clear_proxy_config((LinphoneCore*) nativePtr);
 
-	env->ReleaseStringUTFChars(juserConfig, userConfig);
-	env->ReleaseStringUTFChars(jfactoryConfig, factoryConfig);
+	if (userConfig) env->ReleaseStringUTFChars(juserConfig, userConfig);
+	if (factoryConfig) env->ReleaseStringUTFChars(jfactoryConfig, factoryConfig);
 	return nativePtr;
 }
 extern "C" jlong Java_org_linphone_core_LinphoneCoreImpl_delete(JNIEnv*  env