diff --git a/koordinates/core/kart_task.py b/koordinates/core/kart_task.py
index 69c5293..06af4eb 100644
--- a/koordinates/core/kart_task.py
+++ b/koordinates/core/kart_task.py
@@ -86,7 +86,7 @@ def on_stdout(self, ba):
         """
         Called when the kart process emits messages on stdout
         """
-        val = ba.data().decode('UTF-8')
+        val = ba.data().decode('UTF-8', errors='replace')
         self._stdout_buffer += val
 
         if self._stdout_buffer.endswith('\n') or self._stdout_buffer.endswith(
@@ -182,7 +182,7 @@ def short_result_description(self) -> str:
         ).format(self.title)
 
     def on_stdout(self, ba):
-        val = ba.data().decode('UTF-8')
+        val = ba.data().decode('UTF-8', errors='replace')
 
         counting_regex = re.compile(r'.*Counting objects:?\s*(\d+)%.*')
         receiving_regex = re.compile(r'.*Receiving objects:?\s*(\d+)%.*')