diff --git a/fish_vocoder/test.py b/fish_vocoder/test.py
index 821ef1d..9d0791b 100644
--- a/fish_vocoder/test.py
+++ b/fish_vocoder/test.py
@@ -50,7 +50,8 @@ def main(cfg: DictConfig):
         audios = list(input_path.rglob("*"))
 
     for audio_path in audios:
-        if audio_path.suffix in [".wav", ".flac", ".mp3"]:
+        suffix = audio_path.suffix.lower()
+        if suffix in [".wav", ".flac", ".mp3"]:
             gt_y, sr = librosa.load(audio_path, sr=cfg.model.sampling_rate, mono=False)
 
             # If mono, add a channel dimension
@@ -70,7 +71,7 @@ def main(cfg: DictConfig):
             logger.info(f"gt_y shape: {gt_y.shape}, lengths: {lengths}")
             inputs = model.mel_transforms.input(gt_y.squeeze(1))
 
-        elif audio_path.suffix in [".pt", ".pth"]:
+        elif suffix in [".pt", ".pth"]:
             input_mels = torch.load(audio_path, map_location=model.device).to(
                 torch.float32
             )
diff --git a/fish_vocoder/utils/file.py b/fish_vocoder/utils/file.py
index dc650d1..9830fcb 100644
--- a/fish_vocoder/utils/file.py
+++ b/fish_vocoder/utils/file.py
@@ -52,7 +52,11 @@ def list_files(
     )
 
     if extensions is not None:
-        files = [f for f in files if f.suffix in extensions]
+        # Match case-insensitively. Recorders, phones and camera firmware write
+        # .WAV/.MP3, and Path.suffix preserves that case, so an exact match
+        # dropped those files from the dataset without a warning.
+        extensions = {ext.lower() for ext in extensions}
+        files = [f for f in files if f.suffix.lower() in extensions]
 
     if sort:
         files = sorted(files)
diff --git a/scripts/random_copy.py b/scripts/random_copy.py
index 258a2bf..9ea19b6 100644
--- a/scripts/random_copy.py
+++ b/scripts/random_copy.py
@@ -15,7 +15,11 @@ def random_copy(src: Path, dst: Path, num: int, seed: int):
 
     src, dst = Path(src), Path(dst)
 
-    files = [f for f in src.rglob("*") if f.is_file() and f.suffix in [".wav", ".flac"]]
+    files = [
+        f
+        for f in src.rglob("*")
+        if f.is_file() and f.suffix.lower() in [".wav", ".flac"]
+    ]
     logger.info(f"Found {len(files)} files in {src}")
 
     generator = random.Random(seed)