diff --git a/lib/shared/dm-ops/process-dm-ops.js b/lib/shared/dm-ops/process-dm-ops.js
--- a/lib/shared/dm-ops/process-dm-ops.js
+++ b/lib/shared/dm-ops/process-dm-ops.js
@@ -379,6 +379,12 @@
         recipients,
       );
 
+      // There are no peer devices; the user is sending a message
+      // in a thread with themselves and has only one device.
+      if (outboundP2PMessages.length === 0) {
+        return { result: 'success' };
+      }
+
       const { rawMessageInfos, updateInfos, notificationsCreationData } =
         await dmOpSpecs[op.type].processDMOperation(op, utilities);