diff --git a/_locales/en/messages.json b/_locales/en/messages.json
index c337220a5a22..70547738149e 100644
--- a/_locales/en/messages.json
+++ b/_locales/en/messages.json
@@ -311,6 +311,10 @@
     "message": "You are no longer a member of the group.",
     "description": "Displayed when a user can't send a message because they have left the group"
   },
+  "invalidConversation": {
+    "message": "This group is invalid. Please create a new group.",
+    "description": "Displayed when a user can't send a message because something has gone wrong in the conversation."
+  },
   "scrollDown": {
     "message": "Scroll to bottom of conversation",
     "description": "Alt text for button to take user down to bottom of conversation, shown when user scrolls up"
diff --git a/ts/groups.ts b/ts/groups.ts
index d30b07f29552..ec727a0742ed 100644
--- a/ts/groups.ts
+++ b/ts/groups.ts
@@ -163,6 +163,8 @@ type UpdatesResultType = {
 // Constants
 
 export const MASTER_KEY_LENGTH = 32;
+export const ID_V1_LENGTH = 16;
+export const ID_LENGTH = 32;
 const TEMPORAL_AUTH_REJECTED_CODE = 401;
 const GROUP_ACCESS_DENIED_CODE = 403;
 const SUPPORTED_CHANGE_EPOCH = 0;
diff --git a/ts/models/conversations.ts b/ts/models/conversations.ts
index 61856296d2a5..eb6c5d30636a 100644
--- a/ts/models/conversations.ts
+++ b/ts/models/conversations.ts
@@ -266,7 +266,8 @@ export class ConversationModel extends window.Backbone.Model<
       return false;
     }
 
-    return fromEncodedBinaryToArrayBuffer(groupId).byteLength === 16;
+    const buffer = fromEncodedBinaryToArrayBuffer(groupId);
+    return buffer.byteLength === window.Signal.Groups.ID_V1_LENGTH;
   }
 
   isGroupV2(): boolean {
@@ -277,7 +278,10 @@ export class ConversationModel extends window.Backbone.Model<
 
     const groupVersion = this.get('groupVersion') || 0;
 
-    return groupVersion === 2 && base64ToArrayBuffer(groupId).byteLength === 32;
+    return (
+      groupVersion === 2 &&
+      base64ToArrayBuffer(groupId).byteLength === window.Signal.Groups.ID_LENGTH
+    );
   }
 
   isMemberPending(conversationId: string): boolean {
@@ -822,6 +826,10 @@ export class ConversationModel extends window.Backbone.Model<
     });
   }
 
+  isValid(): boolean {
+    return this.isPrivate() || this.isGroupV1() || this.isGroupV2();
+  }
+
   maybeRepairGroupV2(data: {
     masterKey: string;
     secretParams: string;
diff --git a/ts/views/conversation_view.ts b/ts/views/conversation_view.ts
index 2f2c77be3db5..f74b0b516d47 100644
--- a/ts/views/conversation_view.ts
+++ b/ts/views/conversation_view.ts
@@ -76,6 +76,12 @@ Whisper.LeftGroupToast = Whisper.ToastView.extend({
   },
 });
 
+Whisper.InvalidConversationToast = Whisper.ToastView.extend({
+  render_attributes() {
+    return { toastMessage: window.i18n('invalidConversation') };
+  },
+});
+
 Whisper.OriginalNotFoundToast = Whisper.ToastView.extend({
   render_attributes() {
     return { toastMessage: window.i18n('originalMessageNotFound') };
@@ -2897,6 +2903,10 @@ Whisper.ConversationView = Whisper.View.extend({
         this.model.set({ profileSharing: true });
       }
 
+      if (this.showInvalidMessageToast()) {
+        return;
+      }
+
       const { packId, stickerId } = options;
       this.model.sendStickerMessage(packId, stickerId);
     } catch (error) {
@@ -3030,6 +3040,43 @@ Whisper.ConversationView = Whisper.View.extend({
     });
   },
 
+  showInvalidMessageToast(messageText?: string): boolean {
+    let ToastView;
+
+    if (window.reduxStore.getState().expiration.hasExpired) {
+      ToastView = Whisper.ExpiredToast;
+    }
+    if (!this.model.isValid()) {
+      ToastView = Whisper.InvalidConversationToast;
+    }
+    if (
+      this.model.isPrivate() &&
+      (window.storage.isBlocked(this.model.get('e164')) ||
+        window.storage.isUuidBlocked(this.model.get('uuid')))
+    ) {
+      ToastView = Whisper.BlockedToast;
+    }
+    if (
+      !this.model.isPrivate() &&
+      window.storage.isGroupBlocked(this.model.get('groupId'))
+    ) {
+      ToastView = Whisper.BlockedGroupToast;
+    }
+    if (!this.model.isPrivate() && this.model.get('left')) {
+      ToastView = Whisper.LeftGroupToast;
+    }
+    if (messageText && messageText.length > MAX_MESSAGE_BODY_LENGTH) {
+      ToastView = Whisper.MessageBodyTooLongToast;
+    }
+
+    if (ToastView) {
+      this.showToast(ToastView);
+      return true;
+    }
+
+    return false;
+  },
+
   async sendMessage(message = '', mentions = [], options = {}) {
     this.sendStart = Date.now();
 
@@ -3058,32 +3105,7 @@ Whisper.ConversationView = Whisper.View.extend({
 
     this.model.clearTypingTimers();
 
-    let ToastView;
-    if (window.reduxStore.getState().expiration.hasExpired) {
-      ToastView = Whisper.ExpiredToast;
-    }
-    if (
-      this.model.isPrivate() &&
-      (window.storage.isBlocked(this.model.get('e164')) ||
-        window.storage.isUuidBlocked(this.model.get('uuid')))
-    ) {
-      ToastView = Whisper.BlockedToast;
-    }
-    if (
-      !this.model.isPrivate() &&
-      window.storage.isGroupBlocked(this.model.get('groupId'))
-    ) {
-      ToastView = Whisper.BlockedGroupToast;
-    }
-    if (!this.model.isPrivate() && this.model.get('left')) {
-      ToastView = Whisper.LeftGroupToast;
-    }
-    if (message.length > MAX_MESSAGE_BODY_LENGTH) {
-      ToastView = Whisper.MessageBodyTooLongToast;
-    }
-
-    if (ToastView) {
-      this.showToast(ToastView);
+    if (this.showInvalidMessageToast(message)) {
       this.enableMessageField();
       return;
     }
diff --git a/ts/window.d.ts b/ts/window.d.ts
index da3fabd5157e..ef2aeb1293f0 100644
--- a/ts/window.d.ts
+++ b/ts/window.d.ts
@@ -674,28 +674,30 @@ export type WhisperType = {
   deliveryReceiptBatcher: BatcherType<WhatIsThis>;
   RotateSignedPreKeyListener: WhatIsThis;
 
-  ExpiredToast: typeof Whisper.ToastView;
-  BlockedToast: typeof Whisper.ToastView;
   BlockedGroupToast: typeof Whisper.ToastView;
-  LeftGroupToast: typeof Whisper.ToastView;
-  OriginalNotFoundToast: typeof Whisper.ToastView;
-  OriginalNoLongerAvailableToast: typeof Whisper.ToastView;
+  BlockedToast: typeof Whisper.ToastView;
+  CannotMixImageAndNonImageAttachmentsToast: typeof Whisper.ToastView;
+  DangerousFileTypeToast: typeof Whisper.ToastView;
+  ExpiredToast: typeof Whisper.ToastView;
+  FileSavedToast: typeof Whisper.ToastView;
+  FileSizeToast: any;
   FoundButNotLoadedToast: typeof Whisper.ToastView;
-  VoiceNoteLimit: typeof Whisper.ToastView;
-  VoiceNoteMustBeOnlyAttachmentToast: typeof Whisper.ToastView;
+  InvalidConversationToast: typeof Whisper.ToastView;
+  LeftGroupToast: typeof Whisper.ToastView;
+  MaxAttachmentsToast: typeof Whisper.ToastView;
+  MessageBodyTooLongToast: typeof Whisper.ToastView;
+  OneNonImageAtATimeToast: typeof Whisper.ToastView;
+  OriginalNoLongerAvailableToast: typeof Whisper.ToastView;
+  OriginalNotFoundToast: typeof Whisper.ToastView;
+  PinnedConversationsFullToast: typeof Whisper.ToastView;
+  ReactionFailedToast: typeof Whisper.ToastView;
   TapToViewExpiredIncomingToast: typeof Whisper.ToastView;
   TapToViewExpiredOutgoingToast: typeof Whisper.ToastView;
-  FileSavedToast: typeof Whisper.ToastView;
-  ReactionFailedToast: typeof Whisper.ToastView;
-  MessageBodyTooLongToast: typeof Whisper.ToastView;
-  FileSizeToast: any;
-  UnableToLoadToast: typeof Whisper.ToastView;
-  DangerousFileTypeToast: typeof Whisper.ToastView;
-  OneNonImageAtATimeToast: typeof Whisper.ToastView;
-  CannotMixImageAndNonImageAttachmentsToast: typeof Whisper.ToastView;
-  MaxAttachmentsToast: typeof Whisper.ToastView;
   TimerConflictToast: typeof Whisper.ToastView;
-  PinnedConversationsFullToast: typeof Whisper.ToastView;
+  UnableToLoadToast: typeof Whisper.ToastView;
+  VoiceNoteLimit: typeof Whisper.ToastView;
+  VoiceNoteMustBeOnlyAttachmentToast: typeof Whisper.ToastView;
+
   ConversationLoadingScreen: typeof Whisper.View;
   ConversationView: typeof Whisper.View;
   View: typeof Backbone.View;