diff --git a/_locales/en/messages.json b/_locales/en/messages.json
index 5cd91e36e1..a33ea82efb 100644
--- a/_locales/en/messages.json
+++ b/_locales/en/messages.json
@@ -3862,7 +3862,7 @@
       }
     }
   },
-  "calling__call-notification__button__in-another-call-tooltip": {
+  "calling__in-another-call-tooltip": {
     "message": "You are already in a call",
     "description": "Tooltip in disabled notification button when you're on another call"
   },
diff --git a/ts/components/conversation/CallingNotification.tsx b/ts/components/conversation/CallingNotification.tsx
index 53cef45a2a..f22585bfda 100644
--- a/ts/components/conversation/CallingNotification.tsx
+++ b/ts/components/conversation/CallingNotification.tsx
@@ -137,9 +137,7 @@ function renderCallingNotificationButton(
         ? i18n('calling__call-back')
         : i18n('calling__call-again');
       if (activeCallConversationId) {
-        disabledTooltipText = i18n(
-          'calling__call-notification__button__in-another-call-tooltip'
-        );
+        disabledTooltipText = i18n('calling__in-another-call-tooltip');
         onClick = noop;
       } else {
         onClick = () => {
@@ -159,9 +157,7 @@ function renderCallingNotificationButton(
           onClick = returnToActiveCall;
         } else {
           buttonText = i18n('calling__join');
-          disabledTooltipText = i18n(
-            'calling__call-notification__button__in-another-call-tooltip'
-          );
+          disabledTooltipText = i18n('calling__in-another-call-tooltip');
           onClick = noop;
         }
       } else if (deviceCount >= maxDevices) {
diff --git a/ts/components/conversation/conversation-details/ConversationDetails.stories.tsx b/ts/components/conversation/conversation-details/ConversationDetails.stories.tsx
index dafde3f38e..c63bbf140f 100644
--- a/ts/components/conversation/conversation-details/ConversationDetails.stories.tsx
+++ b/ts/components/conversation/conversation-details/ConversationDetails.stories.tsx
@@ -1,4 +1,4 @@
-// Copyright 2021 Signal Messenger, LLC
+// Copyright 2021-2022 Signal Messenger, LLC
 // SPDX-License-Identifier: AGPL-3.0-only
 
 import * as React from 'react';
@@ -46,6 +46,7 @@ const createProps = (hasGroupLink = false, expireTimer?: number): Props => ({
         expireTimer,
       }
     : conversation,
+  hasActiveCall: false,
   hasGroupLink,
   getPreferredBadge: () => undefined,
   i18n,
diff --git a/ts/components/conversation/conversation-details/ConversationDetails.tsx b/ts/components/conversation/conversation-details/ConversationDetails.tsx
index dc551e4efa..464aab3c3a 100644
--- a/ts/components/conversation/conversation-details/ConversationDetails.tsx
+++ b/ts/components/conversation/conversation-details/ConversationDetails.tsx
@@ -1,10 +1,11 @@
-// Copyright 2021 Signal Messenger, LLC
+// Copyright 2021-2022 Signal Messenger, LLC
 // SPDX-License-Identifier: AGPL-3.0-only
 
 import type { ReactNode } from 'react';
 import React, { useState } from 'react';
 
 import { Button, ButtonIconType, ButtonVariant } from '../../Button';
+import { Tooltip } from '../../Tooltip';
 import type { ConversationType } from '../../../state/ducks/conversations';
 import type { PreferredBadgeSelectorType } from '../../../state/selectors/badges';
 import { assert } from '../../../util/assert';
@@ -62,6 +63,7 @@ export type StateProps = {
   conversation?: ConversationType;
   hasGroupLink: boolean;
   getPreferredBadge: PreferredBadgeSelectorType;
+  hasActiveCall: boolean;
   i18n: LocalizerType;
   isAdmin: boolean;
   isGroup: boolean;
@@ -118,6 +120,7 @@ export const ConversationDetails: React.ComponentType<Props> = ({
   deleteAvatarFromDisk,
   hasGroupLink,
   getPreferredBadge,
+  hasActiveCall,
   i18n,
   isAdmin,
   isGroup,
@@ -339,21 +342,19 @@ export const ConversationDetails: React.ComponentType<Props> = ({
       <div className="ConversationDetails__header-buttons">
         {!conversation.isMe && (
           <>
-            <Button
-              icon={ButtonIconType.video}
+            <ConversationDetailsCallButton
+              disabled={hasActiveCall}
+              i18n={i18n}
               onClick={onOutgoingVideoCallInConversation}
-              variant={ButtonVariant.Details}
-            >
-              {i18n('video')}
-            </Button>
+              type="video"
+            />
             {!isGroup && (
-              <Button
-                icon={ButtonIconType.audio}
+              <ConversationDetailsCallButton
+                disabled={hasActiveCall}
+                i18n={i18n}
                 onClick={onOutgoingAudioCallInConversation}
-                variant={ButtonVariant.Details}
-              >
-                {i18n('audio')}
-              </Button>
+                type="audio"
+              />
             )}
           </>
         )}
@@ -546,3 +547,36 @@ export const ConversationDetails: React.ComponentType<Props> = ({
     </div>
   );
 };
+
+function ConversationDetailsCallButton({
+  disabled,
+  i18n,
+  onClick,
+  type,
+}: Readonly<{
+  disabled: boolean;
+  i18n: LocalizerType;
+  onClick: () => unknown;
+  type: 'audio' | 'video';
+}>) {
+  const button = (
+    <Button
+      disabled={disabled}
+      icon={ButtonIconType[type]}
+      onClick={onClick}
+      variant={ButtonVariant.Details}
+    >
+      {i18n(type)}
+    </Button>
+  );
+
+  if (disabled) {
+    return (
+      <Tooltip content={i18n('calling__in-another-call-tooltip')}>
+        {button}
+      </Tooltip>
+    );
+  }
+
+  return button;
+}
diff --git a/ts/state/ducks/calling.ts b/ts/state/ducks/calling.ts
index c775ba0677..3d065132e4 100644
--- a/ts/state/ducks/calling.ts
+++ b/ts/state/ducks/calling.ts
@@ -1176,6 +1176,11 @@ function startCallingLobby({
       "startCallingLobby: can't start lobby without a conversation"
     );
 
+    strictAssert(
+      !state.calling.activeCallState,
+      "startCallingLobby: can't start lobby if a call is active"
+    );
+
     // The group call device count is considered 0 for a direct call.
     const groupCall = getGroupCall(conversationId, state.calling);
     const groupCallDeviceCount =
diff --git a/ts/state/smart/ConversationDetails.tsx b/ts/state/smart/ConversationDetails.tsx
index 34e08c8529..3150160d19 100644
--- a/ts/state/smart/ConversationDetails.tsx
+++ b/ts/state/smart/ConversationDetails.tsx
@@ -1,4 +1,4 @@
-// Copyright 2021 Signal Messenger, LLC
+// Copyright 2021-2022 Signal Messenger, LLC
 // SPDX-License-Identifier: AGPL-3.0-only
 
 import { connect } from 'react-redux';
@@ -13,6 +13,7 @@ import {
   getConversationByUuidSelector,
 } from '../selectors/conversations';
 import { getGroupMemberships } from '../../util/getGroupMemberships';
+import { getActiveCallState } from '../selectors/calling';
 import { getAreWeASubscriber } from '../selectors/items';
 import { getIntl, getTheme } from '../selectors/user';
 import type { MediaItemType } from '../../types/MediaItem';
@@ -93,6 +94,7 @@ const mapStateToProps = (
       ...getConversationColorAttributes(conversation),
     },
     getPreferredBadge: getPreferredBadgeSelector(state),
+    hasActiveCall: Boolean(getActiveCallState(state)),
     i18n: getIntl(state),
     isAdmin,
     ...groupMemberships,