diff --git a/lib/utils/olm-utils.js b/lib/utils/olm-utils.js
--- a/lib/utils/olm-utils.js
+++ b/lib/utils/olm-utils.js
@@ -128,7 +128,8 @@
   // the corresponding .cpp file
   // at `native/cpp/CommonCpp/CryptoTools/CryptoModule.cpp`.
   invalidSessionVersion: 'INVALID_SESSION_VERSION',
-  alreadyDecrypted: `${OLM_SESSION_ERROR_PREFIX}ALREADY_DECRYPTED_OR_KEYS_SKIPPED`,
+  alreadyDecrypted:
+    OLM_SESSION_ERROR_PREFIX + `ALREADY_DECRYPTED_OR_KEYS_SKIPPED`,
 });
 
 function hasHigherDeviceID(