diff --git a/src/easymatcher_worker.py b/src/easymatcher_worker.py
index e30be43855240bf4929ae48fa0cb584342c1b2ce..b87c2ea874591d9a7cbaac07c06333e238e097d2 100644
--- a/src/easymatcher_worker.py
+++ b/src/easymatcher_worker.py
@@ -31,7 +31,7 @@ class EasymatcherWorker(nlp_ws.NLPWorker):
             document["text"] = _df.read()
 
         with open(file_path, "a", encoding="utf-8") as _f:
-            _f.write(f"{json.dumps(document)}\n")
+            _f.write(json.dumps(document) + "\n")
 
     def process(
         self,
@@ -84,4 +84,4 @@ class EasymatcherWorker(nlp_ws.NLPWorker):
 
         with open(output_path, "w", encoding="utf-8") as _f:
             for out_document in out_documents:
-                _f.write(f"{json.dumps(out_document)}\n")
+                _f.write(json.dumps(out_document) + "\n")