diff --git a/FileTypeChecker.Tests/FileTypeChecker.Tests.csproj b/FileTypeChecker.Tests/FileTypeChecker.Tests.csproj
index 1ce0499..e700479 100644
--- a/FileTypeChecker.Tests/FileTypeChecker.Tests.csproj
+++ b/FileTypeChecker.Tests/FileTypeChecker.Tests.csproj
@@ -125,6 +125,9 @@
     <None Update="files\test-issue-41.xlsx">
       <CopyToOutputDirectory>Always</CopyToOutputDirectory>
     </None>
+    <None Update="files\test-issue-59.xlsx">
+      <CopyToOutputDirectory>Always</CopyToOutputDirectory>
+    </None>
     <None Update="files\file_example_AVI_480_750kB.avi">
       <CopyToOutputDirectory>Always</CopyToOutputDirectory>
     </None>
diff --git a/FileTypeChecker.Tests/FileTypeValidatorTests.cs b/FileTypeChecker.Tests/FileTypeValidatorTests.cs
index 0b90eb8..c3ace14 100644
--- a/FileTypeChecker.Tests/FileTypeValidatorTests.cs
+++ b/FileTypeChecker.Tests/FileTypeValidatorTests.cs
@@ -409,6 +409,7 @@ public void Is_ShouldDistinguishOpenDocumentTypesOnSmallBuffers()
         [TestCase("FileTypeCheckerLogo-150.heic", typeof(HighEfficiencyImageFile))]
         [TestCase("issue311docx.testfile", typeof(MicrosoftOffice365Document))]
         [TestCase("test-issue-41.xlsx", typeof(MicrosoftOffice365Document))]
+        [TestCase("test-issue-59.xlsx", typeof(MicrosoftOffice365Document))]
         [TestCase("file_example_AVI_480_750kB.avi", typeof(AudioVideoInterleaveVideoFormat))]
         [TestCase("file_example_WAV_1MG.wav", typeof(WaveformAudioFileFormat))]
         [TestCase("test.m4a", typeof(M4a))]
diff --git a/FileTypeChecker.Tests/files/test-issue-59.xlsx b/FileTypeChecker.Tests/files/test-issue-59.xlsx
new file mode 100644
index 0000000..964cc6a
Binary files /dev/null and b/FileTypeChecker.Tests/files/test-issue-59.xlsx differ
diff --git a/FileTypeChecker/Types/MicrosoftOffice365Document.cs b/FileTypeChecker/Types/MicrosoftOffice365Document.cs
index 800228d..4be6703 100644
--- a/FileTypeChecker/Types/MicrosoftOffice365Document.cs
+++ b/FileTypeChecker/Types/MicrosoftOffice365Document.cs
@@ -14,6 +14,7 @@ public class MicrosoftOffice365Document : FileType, IFileType
             new(new byte[] { 0x50, 0x4B, 0x03, 0x04, 0x14, 0x00, 0x08, 0x08, 0x08, 0x00 }),
             new(new byte[] { 0x50, 0x4B, 0x03, 0x04, 0x14, 0x00, 0x00, 0x08, 0x08, 0x00 }),
             new(new byte[] { 0x50, 0x4B, 0x03, 0x04, 0x14, 0x00, 0x00, 0x00, 0x08, 0x00 }),
+            new(new byte[] { 0x50, 0x4B, 0x03, 0x04, 0x14, 0x00, 0x06, 0x08, 0x08, 0x00 }),
             new(new byte[] { 0x50, 0x4B, 0x03, 0x04, 0x14, 0x00, 0x06, 0x00 }),
             new(new byte[] { 0x50, 0x4B, 0x03, 0x04, 0x14, 0x00, 0x00, 0x00, 0x00, 0x00, 0xC8 })
         };