diff --git a/src/ViewModels/CommandLog.cs b/src/ViewModels/CommandLog.cs
index f12d27b45..72ea149cb 100644
--- a/src/ViewModels/CommandLog.cs
+++ b/src/ViewModels/CommandLog.cs
@@ -62,6 +62,9 @@ public void AppendLine(string line = null)
             }
             else
             {
+                if (IsComplete || _builder == null)
+                    return;
+
                 var newline = line ?? string.Empty;
                 _builder.AppendLine(newline);