diff --git a/src/main/AndroidManifest.xml b/src/main/AndroidManifest.xml
index 29356fb21..95eb5139c 100644
--- a/src/main/AndroidManifest.xml
+++ b/src/main/AndroidManifest.xml
@@ -34,7 +34,7 @@
     <uses-permission android:name="android.permission.BLUETOOTH" />
     <uses-permission android:name="android.permission.MODIFY_AUDIO_SETTINGS" />
     <uses-permission android:name="android.permission.USE_FULL_SCREEN_INTENT" />
-    <uses-permission android:name="android.permission.SYSTEM_ALERT_WINDOW"/>
+    <uses-permission android:name="android.permission.SYSTEM_ALERT_WINDOW" />
 
     <uses-permission
         android:name="android.permission.READ_PHONE_STATE"
@@ -57,12 +57,12 @@
     <application
         android:allowBackup="false"
         android:appCategory="social"
+        android:hardwareAccelerated="true"
         android:icon="@mipmap/new_launcher"
         android:label="@string/app_name"
         android:networkSecurityConfig="@xml/network_security_configuration"
         android:theme="@style/ConversationsTheme"
         tools:replace="android:label"
-        android:hardwareAccelerated="true"
         tools:targetApi="o">
 
         <meta-data
@@ -291,10 +291,11 @@
         <activity
             android:name=".ui.ChannelDiscoveryActivity"
             android:label="@string/discover_channels" />
-        <activity android:name=".ui.RtpSessionActivity"
-            android:supportsPictureInPicture="true"
-            android:launchMode="singleTask"
-            android:autoRemoveFromRecents="true"/>
+        <activity
+            android:name=".ui.RtpSessionActivity"
+            android:autoRemoveFromRecents="true"
+            android:launchMode="singleInstance"
+            android:supportsPictureInPicture="true" />
     </application>
 
 </manifest>
diff --git a/src/main/java/eu/siacs/conversations/ui/ConversationFragment.java b/src/main/java/eu/siacs/conversations/ui/ConversationFragment.java
index 2c6e2c863..0f47f6936 100644
--- a/src/main/java/eu/siacs/conversations/ui/ConversationFragment.java
+++ b/src/main/java/eu/siacs/conversations/ui/ConversationFragment.java
@@ -1273,11 +1273,17 @@ public class ConversationFragment extends XmppFragment implements EditMessage.Ke
 
 
     private void triggerRtpSession(final String action) {
+        if (activity.xmppConnectionService.getJingleConnectionManager().isBusy()) {
+            Toast.makeText(getActivity(), R.string.only_one_call_at_a_time, Toast.LENGTH_LONG).show();
+            return;
+        }
         final Contact contact = conversation.getContact();
         final Intent intent = new Intent(activity, RtpSessionActivity.class);
         intent.setAction(action);
         intent.putExtra(RtpSessionActivity.EXTRA_ACCOUNT, contact.getAccount().getJid().toEscapedString());
         intent.putExtra(RtpSessionActivity.EXTRA_WITH, contact.getJid().asBareJid().toEscapedString());
+        intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
+        intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TASK);
         startActivity(intent);
     }
 
diff --git a/src/main/java/eu/siacs/conversations/ui/RtpSessionActivity.java b/src/main/java/eu/siacs/conversations/ui/RtpSessionActivity.java
index c3ef71c80..f0cae4e53 100644
--- a/src/main/java/eu/siacs/conversations/ui/RtpSessionActivity.java
+++ b/src/main/java/eu/siacs/conversations/ui/RtpSessionActivity.java
@@ -78,6 +78,7 @@ public class RtpSessionActivity extends XmppActivity implements XmppConnectionSe
 
     @Override
     public void onCreate(Bundle savedInstanceState) {
+        Log.d(Config.LOGTAG, this.getClass().getName() + ".onCreate()");
         super.onCreate(savedInstanceState);
         getWindow().addFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON
                 | WindowManager.LayoutParams.FLAG_DISMISS_KEYGUARD
@@ -87,12 +88,6 @@ public class RtpSessionActivity extends XmppActivity implements XmppConnectionSe
         setSupportActionBar(binding.toolbar);
     }
 
-    @Override
-    public void onStart() {
-        super.onStart();
-        Log.d(Config.LOGTAG, "RtpSessionActivity.onStart()");
-    }
-
     private void endCall(View view) {
         endCall();
     }
@@ -145,7 +140,7 @@ public class RtpSessionActivity extends XmppActivity implements XmppConnectionSe
             if (isMicrophoneAvailable) {
                 return;
             }
-            runOnUiThread(() -> Toast.makeText(this, R.string.microphone_unavailable, Toast.LENGTH_SHORT).show());
+            runOnUiThread(() -> Toast.makeText(this, R.string.microphone_unavailable, Toast.LENGTH_LONG).show());
         }
         ).start();
     }
@@ -206,6 +201,7 @@ public class RtpSessionActivity extends XmppActivity implements XmppConnectionSe
 
     @Override
     public void onNewIntent(final Intent intent) {
+        Log.d(Config.LOGTAG, this.getClass().getName() + ".onNewIntent()");
         super.onNewIntent(intent);
         setIntent(intent);
         if (xmppConnectionService == null) {
diff --git a/src/main/java/eu/siacs/conversations/xmpp/jingle/JingleConnectionManager.java b/src/main/java/eu/siacs/conversations/xmpp/jingle/JingleConnectionManager.java
index 2846fbfaf..0dfb65c97 100644
--- a/src/main/java/eu/siacs/conversations/xmpp/jingle/JingleConnectionManager.java
+++ b/src/main/java/eu/siacs/conversations/xmpp/jingle/JingleConnectionManager.java
@@ -104,7 +104,7 @@ public class JingleConnectionManager extends AbstractConnectionManager {
         return account.isOnion() || mXmppConnectionService.useTorToConnect();
     }
 
-    private boolean isBusy() {
+    public boolean isBusy() {
         for (AbstractJingleConnection connection : this.connections.values()) {
             if (connection instanceof JingleRtpConnection) {
                 return true;
@@ -403,6 +403,9 @@ public class JingleConnectionManager extends AbstractConnectionManager {
                     }
                 }
             }
+            if (isBusy()) {
+                throw new IllegalStateException("There is already a running RTP session. This should have been caught by the UI");
+            }
             final RtpSessionProposal proposal = RtpSessionProposal.of(account, with.asBareJid(), media);
             this.rtpSessionProposals.put(proposal, DeviceDiscoveryState.SEARCHING);
             mXmppConnectionService.notifyJingleRtpConnectionUpdate(
diff --git a/src/main/res/values/strings.xml b/src/main/res/values/strings.xml
index 63a991e76..358d768dd 100644
--- a/src/main/res/values/strings.xml
+++ b/src/main/res/values/strings.xml
@@ -915,6 +915,7 @@
     <string name="audio_call">Audio call</string>
     <string name="video_call">Video call</string>
     <string name="microphone_unavailable">Your microphone is unavailable</string>
+    <string name="only_one_call_at_a_time">You can only have one call at a time.</string>
     <plurals name="view_users">
         <item quantity="one">View %1$d Participant</item>
         <item quantity="other">View %1$d Participants</item>