diff --git a/keyserver/src/creators/message-creator.js b/keyserver/src/creators/message-creator.js
--- a/keyserver/src/creators/message-creator.js
+++ b/keyserver/src/creators/message-creator.js
@@ -456,6 +456,9 @@
             }
             const { generatesNotifs } = messageSpecs[type];
             const messageData = messageDatas[messageIndex];
+            if (!generatesNotifs) {
+              return undefined;
+            }
             const doesGenerateNotif = await generatesNotifs(
               messageInfo,
               messageData,
diff --git a/lib/shared/messages/add-members-message-spec.js b/lib/shared/messages/add-members-message-spec.js
--- a/lib/shared/messages/add-members-message-spec.js
+++ b/lib/shared/messages/add-members-message-spec.js
@@ -152,8 +152,6 @@
     );
   },
 
-  generatesNotifs: async () => undefined,
-
   userIDs(rawMessageInfo: RawAddMembersMessageInfo): $ReadOnlyArray<string> {
     return rawMessageInfo.addedUserIDs;
   },
diff --git a/lib/shared/messages/edit-message-spec.js b/lib/shared/messages/edit-message-spec.js
--- a/lib/shared/messages/edit-message-spec.js
+++ b/lib/shared/messages/edit-message-spec.js
@@ -140,7 +140,5 @@
     return unwrapped;
   },
 
-  generatesNotifs: async () => undefined,
-
   validator: rawEditMessageInfoValidator,
 });
diff --git a/lib/shared/messages/join-thread-message-spec.js b/lib/shared/messages/join-thread-message-spec.js
--- a/lib/shared/messages/join-thread-message-spec.js
+++ b/lib/shared/messages/join-thread-message-spec.js
@@ -119,7 +119,5 @@
     return joinResult(rawMessageInfo.type, rawMessageInfo.threadID);
   },
 
-  generatesNotifs: async () => undefined,
-
   validator: rawJoinThreadMessageInfoValidator,
 });
diff --git a/lib/shared/messages/leave-thread-message-spec.js b/lib/shared/messages/leave-thread-message-spec.js
--- a/lib/shared/messages/leave-thread-message-spec.js
+++ b/lib/shared/messages/leave-thread-message-spec.js
@@ -119,7 +119,5 @@
     return joinResult(rawMessageInfo.type, rawMessageInfo.threadID);
   },
 
-  generatesNotifs: async () => undefined,
-
   validator: rawLeaveThreadMessageInfoValidator,
 });
diff --git a/lib/shared/messages/message-spec.js b/lib/shared/messages/message-spec.js
--- a/lib/shared/messages/message-spec.js
+++ b/lib/shared/messages/message-spec.js
@@ -106,7 +106,7 @@
     rawMessageInfo: RawInfo,
     messageData: Data,
   ) => ?string,
-  +generatesNotifs: (
+  +generatesNotifs?: (
     rawMessageInfo: RawInfo,
     messageData: Data,
     params: GeneratesNotifsParams,
diff --git a/lib/shared/messages/remove-members-message-spec.js b/lib/shared/messages/remove-members-message-spec.js
--- a/lib/shared/messages/remove-members-message-spec.js
+++ b/lib/shared/messages/remove-members-message-spec.js
@@ -152,8 +152,6 @@
     );
   },
 
-  generatesNotifs: async () => undefined,
-
   userIDs(rawMessageInfo: RawRemoveMembersMessageInfo): $ReadOnlyArray<string> {
     return rawMessageInfo.removedUserIDs;
   },
diff --git a/lib/shared/messages/toggle-pin-message-spec.js b/lib/shared/messages/toggle-pin-message-spec.js
--- a/lib/shared/messages/toggle-pin-message-spec.js
+++ b/lib/shared/messages/toggle-pin-message-spec.js
@@ -155,7 +155,5 @@
     return unwrapped;
   },
 
-  generatesNotifs: async () => undefined,
-
   validator: rawTogglePinMessageInfoValidator,
 });
diff --git a/native/root.react.js b/native/root.react.js
--- a/native/root.react.js
+++ b/native/root.react.js
@@ -60,6 +60,7 @@
 
 // Add custom items to expo-dev-menu
 import './dev-menu.js';
+import './types/message-types-validator.js';
 
 if (Platform.OS === 'android') {
   UIManager.setLayoutAnimationEnabledExperimental &&
diff --git a/native/types/message-types-validator.js b/native/types/message-types-validator.js
new file mode 100644
--- /dev/null
+++ b/native/types/message-types-validator.js
@@ -0,0 +1,29 @@
+// @flow
+import { Alert } from 'react-native';
+
+import { messageSpecs } from 'lib/shared/messages/message-specs.js';
+import { messageTypes } from 'lib/types/message-types-enum.js';
+
+import { commConstants } from '../native-modules.js';
+
+if (__DEV__) {
+  const messageTypesCpp = new Set(commConstants.NATIVE_MESSAGE_TYPES);
+  const missingMessageTypesCpp = [];
+  for (const messageName in messageTypes) {
+    const messageType = messageTypes[messageName];
+    if (
+      messageSpecs[messageType]?.generatesNotifs &&
+      !messageTypesCpp.has(messageType)
+    ) {
+      missingMessageTypesCpp.push(messageName);
+    }
+  }
+
+  if (missingMessageTypesCpp.length !== 0) {
+    Alert.alert(
+      'C++ MessageSpecs missing',
+      'C++ MessageSpec implementation missing for message types: ' +
+        missingMessageTypesCpp.join(', '),
+    );
+  }
+}