diff --git a/packages/core/src/store.ts b/packages/core/src/store.ts
--- a/packages/core/src/store.ts
+++ b/packages/core/src/store.ts
@@ -267,7 +267,7 @@
     learned = true
   }
   const signers = unionSigners(held.deviceKeyIds, incoming.deviceKeyIds)
-  if (signers && signers.join(' ') !== held.deviceKeyIds?.join(' ')) {
+  if (signers && signers.join('\u0000') !== held.deviceKeyIds?.join('\u0000')) {
     held.deviceKeyIds = signers
     learned = true
   }