diff --git a/packages/common/nbstore/src/impls/cloud/blob.ts b/packages/common/nbstore/src/impls/cloud/blob.ts
index cec0a5c9f6..c317f11161 100644
--- a/packages/common/nbstore/src/impls/cloud/blob.ts
+++ b/packages/common/nbstore/src/impls/cloud/blob.ts
@@ -116,7 +116,10 @@ export class CloudBlobStorage extends BlobStorageBase {
         throw new OverSizeError(this.humanReadableBlobSizeLimitCache);
       }
       if (userFriendlyError.is('CONTENT_TOO_LARGE')) {
-        throw new OverSizeError(this.humanReadableBlobSizeLimitCache);
+        throw new OverSizeError(
+          null,
+          'Upload stopped by network proxy: file size exceeds the set limit.'
+        );
       }
       throw err;
     }
diff --git a/packages/common/nbstore/src/storage/errors/over-size.ts b/packages/common/nbstore/src/storage/errors/over-size.ts
index bbedb1a2dd..abf163b3c9 100644
--- a/packages/common/nbstore/src/storage/errors/over-size.ts
+++ b/packages/common/nbstore/src/storage/errors/over-size.ts
@@ -1,6 +1,10 @@
 export class OverSizeError extends Error {
-  constructor(limit: string | null) {
-    const formattedLimit = limit ? `${limit} ` : '';
-    super(`File size exceeds the ${formattedLimit}limit.`);
+  constructor(limit: string | null, message?: string) {
+    if (message) {
+      super(message);
+    } else {
+      const formattedLimit = limit ? `${limit} ` : '';
+      super(`File size exceeds the ${formattedLimit}limit.`);
+    }
   }
 }