diff --git a/src/tscut/cutting.py b/src/tscut/cutting.py
index b8f5313..24a1df2 100644
--- a/src/tscut/cutting.py
+++ b/src/tscut/cutting.py
@@ -128,14 +128,14 @@ def cut_recording(media: PreparedMedia, options: ProcessingOptions,
         head_frames = get_nearest_iframe(options.tools_paths['ffprobe'], media.movie, ts1,
                                          before=False)
         if head_frames is None:
-            raise InvalidMediaError(f"Impossible to retrieve first I-frame")
+            raise InvalidMediaError("Impossible to retrieve first I-frame")
 
         # Get the nearest I-frame whose timestamp ...
         # TODO: wrong here ...
         tail_frames = get_nearest_iframe(options.tools_paths['ffprobe'], media.movie,
                                          ts2, before=True)
         if tail_frames is None:
-            raise InvalidMediaError(f"Impossible to retrieve last I-frame")
+            raise InvalidMediaError("Impossible to retrieve last I-frame")
 
         nb_head_frames, head_iframe = head_frames
         nb_tail_frames, tail_iframe = tail_frames
@@ -147,10 +147,10 @@ def cut_recording(media: PreparedMedia, options: ProcessingOptions,
 
         head_iframe_ts = get_ts_frame(head_iframe)
         if head_iframe_ts is None:
-            raise InvalidMediaError(f"Impossible to retrieve timestamp of first i-frame.")
+            raise InvalidMediaError("Impossible to retrieve timestamp of first i-frame.")
         tail_iframe_ts = get_ts_frame(tail_iframe)
         if tail_iframe_ts is None:
-            raise InvalidMediaError(f"Impossible to retrieve timestamp of final i-frame.")
+            raise InvalidMediaError("Impossible to retrieve timestamp of final i-frame.")
 
         checks.append(pos+head_iframe_ts-ts1)
 
@@ -298,7 +298,7 @@ def cut_recording(media: PreparedMedia, options: ProcessingOptions,
         try:
             full_h264 = open(f'{media.basename}-full.h264', 'wb+')
         except OSError:
-            raise TemporaryFileError(f"Impossible to create file full H264 stream.")
+            raise TemporaryFileError("Impossible to create file full H264 stream.")
 
         logger.info('Merging all H264 tracks')
         concatenate_h264_parts(h264parts=h264parts, output=full_h264)
@@ -307,7 +307,7 @@ def cut_recording(media: PreparedMedia, options: ProcessingOptions,
         try:
             full_h264_ts = open(f'{media.basename}-ts.txt', 'w+', encoding='utf8')
         except OSError:
-            raise TemporaryFileError(f"Impossible to create file containing all video timestamps.")
+            raise TemporaryFileError("Impossible to create file containing all video timestamps.")
 
         logger.info('Merging H264 timestamps')
         concatenate_h264_ts_parts(h264_ts_parts=h264_ts, output=full_h264_ts)
diff --git a/src/tscut/pipeline.py b/src/tscut/pipeline.py
index 445c2ed..b512874 100644
--- a/src/tscut/pipeline.py
+++ b/src/tscut/pipeline.py
@@ -138,7 +138,7 @@ def process_recording(options: ProcessingOptions, temporaries: TemporaryFiles) -
                 main_video = None
 
     if main_video is None:
-        raise InvalidMediaError(f"Impossible to find main video stream.")
+        raise InvalidMediaError("Impossible to find main video stream.")
 
     # We retrieve the main private codec data
     _, main_codec_private_data = get_codec_private_data_from_mkv(
diff --git a/src/tscut/tools/mkvtoolnix.py b/src/tscut/tools/mkvtoolnix.py
index a8bfe63..c0c9e7f 100644
--- a/src/tscut/tools/mkvtoolnix.py
+++ b/src/tscut/tools/mkvtoolnix.py
@@ -129,7 +129,7 @@ def change_codec_private_data(mkvinfo_path:str, input_file: IO[bytes],
     logger.info('Current size of file: %d', current_length)
     position, current_data = get_codec_private_data_from_mkv(mkvinfo_path, input_file)
     if position is None or current_data is None:
-        raise InvalidMediaError(f"Impossible to retrieve private data from file")
+        raise InvalidMediaError("Impossible to retrieve private data from file")
     current_data_length = len(current_data)
     future_length = current_length - current_data_length + len(codec_data)
     logger.info('Expected size of file: %d', future_length)
@@ -147,7 +147,7 @@ def change_codec_private_data(mkvinfo_path:str, input_file: IO[bytes],
             break
 
     if not found:
-        raise InvalidMediaError(f"Impossible to retrieve the key of codec private data")
+        raise InvalidMediaError("Impossible to retrieve the key of codec private data")
 
     if current_length < future_length:
         lseek(infd, position+current_data_length, SEEK_SET)