diff --git a/keyserver/src/cron/backups.js b/keyserver/src/cron/backups.js
--- a/keyserver/src/cron/backups.js
+++ b/keyserver/src/cron/backups.js
@@ -265,6 +265,9 @@
 
   const sortedBackupInfos = await getSortedBackupInfos();
   const mostRecentBackup = sortedBackupInfos.pop();
+  if (!mostRecentBackup) {
+    return;
+  }
   let bytesLeft = maxDirSizeMiB * 1024 * 1024 - mostRecentBackup.bytes;
 
   const deleteBackupPromises = [];
diff --git a/lib/shared/radix-tree.js b/lib/shared/radix-tree.js
--- a/lib/shared/radix-tree.js
+++ b/lib/shared/radix-tree.js
@@ -97,7 +97,11 @@
       +partLeft: string,
     }> = [{ node: this.root, partLeft: prefix }];
     while (stack.length > 0) {
-      const { node, partLeft: prevPartLeft } = stack.pop();
+      const top = stack.pop();
+      if (!top) {
+        break;
+      }
+      const { node, partLeft: prevPartLeft } = top;
       if (node.leaf) {
         for (const value of node.values) {
           result.add(value);
diff --git a/lib/shared/threads/protocols/dm-thread-protocol.js b/lib/shared/threads/protocols/dm-thread-protocol.js
--- a/lib/shared/threads/protocols/dm-thread-protocol.js
+++ b/lib/shared/threads/protocols/dm-thread-protocol.js
@@ -940,6 +940,7 @@
   threadInfo: ThickRawThreadInfo,
 ): CreateThickRawThreadInfoInput {
   const roleID = Object.keys(threadInfo.roles).pop();
+  invariant(roleID, 'roleID must be set');
   const thickThreadType = assertThickThreadType(threadInfo.type);
   return {
     threadID: threadInfo.id,
diff --git a/lib/utils/cookie-utils.js b/lib/utils/cookie-utils.js
--- a/lib/utils/cookie-utils.js
+++ b/lib/utils/cookie-utils.js
@@ -1,5 +1,7 @@
 // @flow
 
+import invariant from 'invariant';
+
 function parseCookies(header: string): { +[string]: string } {
   const values = header.split(';').map(v => v.split('='));
 
@@ -13,6 +15,7 @@
 
 function getCookieIDFromCookie(cookie: string): string {
   const cookieString = cookie.split('=').pop();
+  invariant(cookieString, 'invalid cookie');
   const [cookieID] = cookieString.split(':');
   return cookieID;
 }
diff --git a/native/media/media-cache.js b/native/media/media-cache.js
--- a/native/media/media-cache.js
+++ b/native/media/media-cache.js
@@ -20,6 +20,7 @@
 function basenameFromBlobURI(blobURI: string) {
   // if blobURI is a file URI or path, use the last segment of the path
   const filename = blobURI.split('/').pop();
+  invariant(filename, 'invalid blob URI');
   return filenameWithoutExtension(filename);
 }
 
diff --git a/native/navigation/modal-pruner.react.js b/native/navigation/modal-pruner.react.js
--- a/native/navigation/modal-pruner.react.js
+++ b/native/navigation/modal-pruner.react.js
@@ -81,6 +81,7 @@
     const toResolve = [...presenting];
     while (toResolve.length > 0) {
       const presentee = toResolve.pop();
+      invariant(presentee, 'could not find presentee');
       const dependencyInfo = dependencyMap.get(presentee);
       invariant(dependencyInfo, 'could not find presentee');
       dependencyInfo.status = 'resolved';