diff --git a/lib/configuration/variables/sources/file.js b/lib/configuration/variables/sources/file.js
index <HASH>..<HASH> 100644
--- a/lib/configuration/variables/sources/file.js
+++ b/lib/configuration/variables/sources/file.js
@@ -169,8 +169,9 @@ module.exports = {
           throw new ServerlessError(
             `Cannot resolve "${address}" out of "${path.basename(
               filePath
-            )}": Resolved a JS function not confirmed to work with a new parser, ` +
-              'falling back to old resolver',
+            )}": Approached a JS function resolver, confirm it's updated to work with a ` +
+              'new parser by setting "variablesResolutionMode: 20210326" in service config. ' +
+              'Falling back to old resolver',
             'FILE_CONTENT_RESOLUTION_ERROR'
           );
         }
fix(Variables): Unify error messaging for function resolvers