diff --git a/sorl/thumbnail/engines/convert_engine.py b/sorl/thumbnail/engines/convert_engine.py
index 19bf9e61e..54f736083 100644
--- a/sorl/thumbnail/engines/convert_engine.py
+++ b/sorl/thumbnail/engines/convert_engine.py
@@ -110,7 +110,7 @@ def _get_exif_orientation(self, image):
         p = subprocess.Popen(args, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
         p.wait()
         result = p.stdout.read().strip()
-        if result and result != 'unknown':
+        if result and result != b'unknown':
             return int(result)
         else:
             return None