diff --git a/unshackle/core/drm/playready.py b/unshackle/core/drm/playready.py
index a26428a..b1fcea0 100644
--- a/unshackle/core/drm/playready.py
+++ b/unshackle/core/drm/playready.py
@@ -338,7 +338,7 @@ class PlayReady:
         ]
 
         try:
-            subprocess.run(cmd, check=True, stdout=subprocess.PIPE, stderr=subprocess.PIPE, text=True)
+            subprocess.run(cmd, check=True, stdout=subprocess.PIPE, stderr=subprocess.PIPE, text=True, encoding='utf-8')
         except subprocess.CalledProcessError as e:
             error_msg = e.stderr if e.stderr else f"mp4decrypt failed with exit code {e.returncode}"
             raise subprocess.CalledProcessError(e.returncode, cmd, output=e.stdout, stderr=error_msg)
diff --git a/unshackle/core/drm/widevine.py b/unshackle/core/drm/widevine.py
index 6c3d683..7fee1c9 100644
--- a/unshackle/core/drm/widevine.py
+++ b/unshackle/core/drm/widevine.py
@@ -289,7 +289,7 @@ class Widevine:
         ]
 
         try:
-            subprocess.run(cmd, check=True, stdout=subprocess.PIPE, stderr=subprocess.PIPE, text=True)
+            subprocess.run(cmd, check=True, stdout=subprocess.PIPE, stderr=subprocess.PIPE, text=True, encoding='utf-8')
         except subprocess.CalledProcessError as e:
             error_msg = e.stderr if e.stderr else f"mp4decrypt failed with exit code {e.returncode}"
             raise subprocess.CalledProcessError(e.returncode, cmd, output=e.stdout, stderr=error_msg)