diff --git a/app/build.gradle b/app/build.gradle
index 682a6a26..38f7fd18 100644
--- a/app/build.gradle
+++ b/app/build.gradle
@@ -8,8 +8,8 @@ android {
         applicationId = 'com.tutpro.baresip'
         minSdkVersion 21
         targetSdkVersion 27
-        versionCode = 27
-        versionName = '3.1.0'
+        versionCode = 28
+        versionName = '3.1.1'
         externalNativeBuild {
             cmake {
                 cFlags '-DHAVE_INTTYPES_H'
diff --git a/app/src/main/cpp/baresip.c b/app/src/main/cpp/baresip.c
index 9f845e54..0da4d3bd 100644
--- a/app/src/main/cpp/baresip.c
+++ b/app/src/main/cpp/baresip.c
@@ -951,7 +951,8 @@ Java_com_tutpro_baresip_MainActivity_call_1start_1audio(JNIEnv *env, jobject thi
     struct call *call = (struct call *)strtoul(native_call, NULL, 10);
     LOGD("starting audio of call %s\n", native_call);
     re_thread_enter();
-    audio_start(call_audio(call));
+    struct audio *a = call_audio(call);
+    if (!audio_started(a)) audio_start(a);
     re_thread_leave();
     (*env)->ReleaseStringUTFChars(env, javaCall, native_call);
     return;
@@ -963,7 +964,8 @@ Java_com_tutpro_baresip_MainActivity_call_1stop_1audio(JNIEnv *env, jobject thiz
     struct call *call = (struct call *)strtoul(native_call, NULL, 10);
     LOGD("stopping audio of call %s\n", native_call);
     re_thread_enter();
-    audio_stop(call_audio(call));
+    struct audio *a = call_audio(call);
+    if (audio_started(a)) audio_stop(a);
     re_thread_leave();
     (*env)->ReleaseStringUTFChars(env, javaCall, native_call);
     return;