diff --git a/arcor2/docstring.py b/arcor2/docstring.py
index eb82ad38..d74cff6f 100644
--- a/arcor2/docstring.py
+++ b/arcor2/docstring.py
@@ -59,7 +59,7 @@ def trim(docstring):
 
 
 def reindent(string):
-    return "\n".join(l.strip() for l in string.strip().split("\n"))
+    return "\n".join(line.strip() for line in string.strip().split("\n"))
 
 
 def parse_docstring(docstring):
diff --git a/arcor2/helpers.py b/arcor2/helpers.py
index a5017c5c..e08a88d0 100644
--- a/arcor2/helpers.py
+++ b/arcor2/helpers.py
@@ -308,6 +308,6 @@ def type_def_from_source(source: str, type_name: str, output_type: Type[T]) -> T
         raise TypeDefException(f"Source does not contain class named '{type_name}'.")
 
     if not issubclass(cls_def, output_type):
-        raise TypeDefException(f"Class is not of expected type.")
+        raise TypeDefException("Class is not of expected type.")
 
     return cls_def
diff --git a/arcor2/nodes/build.py b/arcor2/nodes/build.py
index ce7bbef0..8b04897b 100755
--- a/arcor2/nodes/build.py
+++ b/arcor2/nodes/build.py
@@ -228,7 +228,7 @@ def main():
 
     swaggerui_blueprint = get_swaggerui_blueprint(
         SWAGGER_URL,  # Swagger UI static files will be mapped to '{SWAGGER_URL}/dist/'
-        f"./api/swagger.json"
+        "./api/swagger.json"
     )
 
     # Register blueprint at URL
diff --git a/arcor2/nodes/execution_proxy.py b/arcor2/nodes/execution_proxy.py
index 117e1a8f..be9ee5bd 100755
--- a/arcor2/nodes/execution_proxy.py
+++ b/arcor2/nodes/execution_proxy.py
@@ -412,7 +412,7 @@ def main():
 
     swaggerui_blueprint = get_swaggerui_blueprint(
         SWAGGER_URL,  # Swagger UI static files will be mapped to '{SWAGGER_URL}/dist/'
-        f"./api/swagger.json"
+        "./api/swagger.json"
     )
 
     # Register blueprint at URL
diff --git a/arcor2/rest.py b/arcor2/rest.py
index 4f462443..e54c61a0 100644
--- a/arcor2/rest.py
+++ b/arcor2/rest.py
@@ -97,7 +97,7 @@ def _send(url: str, op: Callable, data: OptionalData = None,
         resp = op(url, data=json.dumps(d), timeout=TIMEOUT, headers={'Content-Type': 'application/json'},
                   params=params)
     except requests.exceptions.RequestException as e:
-        raise RestException(f"Catastrophic system error.", str(e)) from e
+        raise RestException("Catastrophic system error.", str(e)) from e
 
     handle_response(resp)
 
@@ -162,7 +162,7 @@ def delete(url: str):
     try:
         resp = SESSION.delete(url, timeout=TIMEOUT)
     except requests.exceptions.RequestException as e:
-        raise RestException(f"Catastrophic system error.", str(e)) from e
+        raise RestException("Catastrophic system error.", str(e)) from e
 
     handle_response(resp)
 
@@ -192,7 +192,7 @@ def _get_response(url: str, body: Optional[JsonSchemaMixin] = None, params: Para
     try:
         resp = SESSION.get(url, timeout=TIMEOUT, data=body_dict, params=params)
     except requests.exceptions.RequestException as e:
-        raise RestException(f"Catastrophic system error.", str(e)) from e
+        raise RestException("Catastrophic system error.", str(e)) from e
 
     handle_response(resp)
 
diff --git a/arcor2/server/rpc/scene.py b/arcor2/server/rpc/scene.py
index c51a80a0..f2c37b03 100644
--- a/arcor2/server/rpc/scene.py
+++ b/arcor2/server/rpc/scene.py
@@ -382,7 +382,7 @@ async def rename_object_cb(req: rpc.scene.RenameObjectRequest) -> \
 
     for obj_name in glob.SCENE.object_names():
         if obj_name == req.args.new_name:
-            return False, f"Object name already exists."
+            return False, "Object name already exists."
 
     target_obj.name = req.args.new_name