diff --git a/SpreadCheetah.Test/Tests/SpreadsheetNoteTests.cs b/SpreadCheetah.Test/Tests/SpreadsheetNoteTests.cs
index ad04c50d..37a06325 100644
--- a/SpreadCheetah.Test/Tests/SpreadsheetNoteTests.cs
+++ b/SpreadCheetah.Test/Tests/SpreadsheetNoteTests.cs
@@ -156,6 +156,25 @@ public async Task Spreadsheet_AddNote_ThrowsOnTooLongText(int textLength, bool e
         Assert.Equal(exceptionExpected, exception is ArgumentException);
     }
 
+    [Theory]
+    [InlineData(null)]
+    [InlineData("")]
+    [InlineData(" ")]
+    [InlineData("A")]
+    [InlineData("A0")]
+    [InlineData("A1:A2")]
+    [InlineData("$A$1")]
+    public async Task Spreadsheet_AddNote_InvalidReference(string reference)
+    {
+        // Arrange
+        using var stream = new MemoryStream();
+        await using var spreadsheet = await Spreadsheet.CreateNewAsync(stream);
+        await spreadsheet.StartWorksheetAsync("Sheet");
+
+        // Act & Assert
+        Assert.ThrowsAny<ArgumentException>(() => spreadsheet.AddNote(reference, "My note"));
+    }
+
     [Theory]
     [InlineData("A1", "1.2pt")]
     [InlineData("A2", "8.4pt")]