diff --git a/judge/views/submission.py b/judge/views/submission.py
index d130062..faa4d60 100644
--- a/judge/views/submission.py
+++ b/judge/views/submission.py
@@ -156,8 +156,10 @@ def get_cases_data(submission):
     for case in testcases:
         if case.type != 'C': continue
         count += 1
-        problem_data[count] = {'input': case_data[case.input_file],
-                                   'answer': case_data[case.output_file]}
+        problem_data[count] = {
+            'input': case_data[case.input_file] if case.input_file else '',
+            'answer': case_data[case.output_file] if case.output_file else '',
+        }
 
     return problem_data