1 files changed, 4 insertions, 0 deletions
diff --git a/PBNFile.cs b/PBNFile.cs
index bec7fcd..5526623 100644
--- a/PBNFile.cs
+++ b/PBNFile.cs
@@ -58,6 +58,10 @@ namespace BCDD
 
         public void Save()
         {
+            if (this.outputFile == null)
+            {
+                throw new IOException("No boards written to PBN file, unable to save it.");
+            }
             this.outputFile.Flush();
             this.outputFile.Close();
             File.Delete(this.filename);