diff --git a/OemLoader/MainWindow.cs b/OemLoader/MainWindow.cs
index 8469d6c..2c3b000 100644
--- a/OemLoader/MainWindow.cs
+++ b/OemLoader/MainWindow.cs
@@ -72,8 +72,15 @@ public class MainWindow(string title)
                 try
                 {
                     _oem = OemDataLine.ReadFile(_filename.ToString());
-                    _sliderTicks = _oem.First().Epoch.Ticks;
-                    _errorMessage = null;
+                    if (_oem is not null)
+                    {
+                        _sliderTicks = _oem.First().Epoch.Ticks;
+                        _errorMessage = null;   
+                    }
+                    else
+                    {
+                        _errorMessage = "Could not find any ephemeris data in file";
+                    }
                 }
                 catch (Exception e)
                 {
diff --git a/OemLoader/OemDataLine.cs b/OemLoader/OemDataLine.cs
index 210744f..98c4670 100644
--- a/OemLoader/OemDataLine.cs
+++ b/OemLoader/OemDataLine.cs
@@ -42,7 +42,7 @@ public partial struct OemDataLine
     [GeneratedRegex(@"^\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}(.\d{3})?(\s+-?\d+(.\d+)){6,}$")]
     private static partial Regex OemLineRegex { get; }
     
-    public static List<OemDataLine> ReadFile(string path)
+    public static List<OemDataLine>? ReadFile(string path)
     {
         var data = new List<OemDataLine>();
         var lines = File.ReadAllLines(path);
@@ -54,6 +54,6 @@ public partial struct OemDataLine
             }
         }
 
-        return data;
+        return data.Count == 0 ? null : data;
     }
 }
\ No newline at end of file