diff --git a/Lib/test/test_gdb.py b/Lib/test/test_gdb.py
index 489ceef..4cff870 100644
--- a/Lib/test/test_gdb.py
+++ b/Lib/test/test_gdb.py
@@ -59,7 +59,7 @@
         out, err = subprocess.Popen(
             args, stdout=subprocess.PIPE, stderr=subprocess.PIPE,
             ).communicate()
-        return out.decode('utf-8'), err.decode('utf-8')
+        return out.decode('utf-8', 'replace'), err.decode('utf-8', 'replace')
 
     def get_stack_trace(self, source=None, script=None,
                         breakpoint=BREAKPOINT_FN,