diff --git a/src/SIL.Machine/Corpora/FileParatextProjectFileHandler.cs b/src/SIL.Machine/Corpora/FileParatextProjectFileHandler.cs
index 3d336e3f..df6dd045 100644
--- a/src/SIL.Machine/Corpora/FileParatextProjectFileHandler.cs
+++ b/src/SIL.Machine/Corpora/FileParatextProjectFileHandler.cs
@@ -14,12 +14,23 @@ public FileParatextProjectFileHandler(string projectDir)
 
         public bool Exists(string fileName)
         {
-            return File.Exists(Path.Combine(_projectDir, fileName));
+            return Directory
+                .EnumerateFiles(_projectDir)
+                .Any(f => Path.GetFileName(f).Equals(fileName, System.StringComparison.InvariantCultureIgnoreCase));
         }
 
         public Stream Open(string fileName)
         {
-            return File.OpenRead(Path.Combine(_projectDir, fileName));
+            return File.OpenRead(
+                Path.Combine(
+                    _projectDir,
+                    Directory
+                        .EnumerateFiles(_projectDir)
+                        .FirstOrDefault(f =>
+                            Path.GetFileName(f).Equals(fileName, System.StringComparison.InvariantCultureIgnoreCase)
+                        )
+                )
+            );
         }
 
         public UsfmStylesheet CreateStylesheet(string fileName)
diff --git a/src/SIL.Machine/Corpora/ZipParatextProjectFileHandler.cs b/src/SIL.Machine/Corpora/ZipParatextProjectFileHandler.cs
index 00338dda..2b614bbc 100644
--- a/src/SIL.Machine/Corpora/ZipParatextProjectFileHandler.cs
+++ b/src/SIL.Machine/Corpora/ZipParatextProjectFileHandler.cs
@@ -16,12 +16,16 @@ public ZipParatextProjectFileHandler(ZipArchive archive)
 
         public bool Exists(string fileName)
         {
-            return _archive.GetEntry(fileName) != null;
+            return _archive.Entries.Any(e =>
+                e.FullName.Equals(fileName, System.StringComparison.InvariantCultureIgnoreCase)
+            );
         }
 
         public Stream Open(string fileName)
         {
-            ZipArchiveEntry entry = _archive.GetEntry(fileName);
+            ZipArchiveEntry entry = _archive.Entries.FirstOrDefault(e =>
+                e.FullName.Equals(fileName, System.StringComparison.InvariantCultureIgnoreCase)
+            );
             if (entry == null)
                 return null;
             return entry.Open();
@@ -29,7 +33,9 @@ public Stream Open(string fileName)
 
         public string Find(string extension)
         {
-            ZipArchiveEntry entry = _archive.Entries.FirstOrDefault(e => e.FullName.EndsWith(extension));
+            ZipArchiveEntry entry = _archive.Entries.FirstOrDefault(e =>
+                e.FullName.EndsWith(extension, System.StringComparison.InvariantCultureIgnoreCase)
+            );
             if (entry == null)
                 return null;
             return entry.FullName;
diff --git a/tests/SIL.Machine.Tests/Corpora/TestData/usfm/Tes/custom.vrs b/tests/SIL.Machine.Tests/Corpora/TestData/usfm/Tes/Custom.vrs
similarity index 100%
rename from tests/SIL.Machine.Tests/Corpora/TestData/usfm/Tes/custom.vrs
rename to tests/SIL.Machine.Tests/Corpora/TestData/usfm/Tes/Custom.vrs