diff --git a/ImageDescriber.Test/ImageScannerTests.cs b/ImageDescriber.Test/ImageScannerTests.cs
index a2b46d5..816cfad 100644
--- a/ImageDescriber.Test/ImageScannerTests.cs
+++ b/ImageDescriber.Test/ImageScannerTests.cs
@@ -126,4 +126,30 @@ public void ScanForImagesRecognizesAllSupportedExtensions()
 			Directory.Delete(tempDir, true);
 		}
 	}
+
+	[TestMethod]
+	public void ScanForImagesMatchesExtensionsCaseInsensitively()
+	{
+		string tempDir = Path.Combine(Path.GetTempPath(), Guid.NewGuid().ToString());
+		Directory.CreateDirectory(tempDir);
+
+		try
+		{
+			File.WriteAllBytes(Path.Combine(tempDir, "IMG_0001.JPG"), [0xFF, 0xD8]);
+			File.WriteAllBytes(Path.Combine(tempDir, "screenshot.Png"), [0x89, 0x50]);
+			File.WriteAllBytes(Path.Combine(tempDir, "photo.jpeg"), [0xFF, 0xD8]);
+			File.WriteAllBytes(Path.Combine(tempDir, "scan.TIFF"), [0x49, 0x49]);
+			File.WriteAllText(Path.Combine(tempDir, "NOTES.TXT"), "text");
+
+			IReadOnlyList<AbsoluteFilePath> results = ImageScanner.ScanForImages(tempDir.As<AbsoluteDirectoryPath>());
+
+			string[] names = [.. results.Select(r => Path.GetFileName(r.WeakString)).Order(StringComparer.Ordinal)];
+			string[] expected = ["IMG_0001.JPG", "photo.jpeg", "scan.TIFF", "screenshot.Png"];
+			CollectionAssert.AreEqual(expected, names);
+		}
+		finally
+		{
+			Directory.Delete(tempDir, true);
+		}
+	}
 }
diff --git a/ImageDescriber/ImageScanner.cs b/ImageDescriber/ImageScanner.cs
index 369a042..b9740de 100644
--- a/ImageDescriber/ImageScanner.cs
+++ b/ImageDescriber/ImageScanner.cs
@@ -39,7 +39,9 @@ internal static IReadOnlyList<AbsoluteFilePath> ScanForImages(AbsoluteDirectoryP
 				continue;
 			}
 
-			if (ImageExtensions.Contains(ext.As<FileExtension>()))
+			// FileExtension compares ordinally, and cameras and Windows tools write .JPG/.PNG,
+			// so fold to the lower-case form the set holds before looking it up.
+			if (ImageExtensions.Contains(ext.ToLowerInvariant().As<FileExtension>()))
 			{
 				imageFiles.Add(file.As<AbsoluteFilePath>());
 			}