diff --git a/src/BCC.Web/Services/CheckRunSubmissionService.cs b/src/BCC.Web/Services/CheckRunSubmissionService.cs
index d46ba13..d566ccd 100644
--- a/src/BCC.Web/Services/CheckRunSubmissionService.cs
+++ b/src/BCC.Web/Services/CheckRunSubmissionService.cs
@@ -1,5 +1,6 @@
 using System;
 using System.IO.Abstractions;
+using System.Text;
 using System.Threading.Tasks;
 using BCC.Core.Model.CheckRunSubmission;
 using JetBrains.Annotations;
@@ -56,6 +57,15 @@ public Task<CheckRun> SubmitAsync([NotNull] string owner, [NotNull] string repos
 
             var createCheckRun = JsonConvert.DeserializeObject<CreateCheckRun>(readAllText);
 
+            if (createCheckRun.Summary != null)
+            {
+                var byteCount = Encoding.Unicode.GetByteCount(createCheckRun.Summary) / 1024.0;
+                if (byteCount > 128.0)
+                {
+                    throw new InvalidOperationException();
+                }
+            }
+
             return _gitHubAppModelService.SubmitCheckRunAsync(owner, repository, sha, createCheckRun);
         }
     }