diff --git a/machine/corpora/paratext_project_settings.py b/machine/corpora/paratext_project_settings.py
index 04820cf5..b4ab51fc 100644
--- a/machine/corpora/paratext_project_settings.py
+++ b/machine/corpora/paratext_project_settings.py
@@ -31,7 +31,10 @@ class ParatextProjectSettings:
 
     def get_book_id(self, file_name: str) -> Optional[str]:
         """Returns None when the file name doesn't match the pattern of a book file name for the project."""
-        if not file_name.startswith(self.file_name_prefix) or not file_name.endswith(self.file_name_suffix):
+        file_name_casefolded = file_name.casefold()
+        if not file_name_casefolded.startswith(self.file_name_prefix.casefold()) or not file_name_casefolded.endswith(
+            self.file_name_suffix.casefold()
+        ):
             return None
 
         book_part: str = file_name[len(self.file_name_prefix) : -len(self.file_name_suffix)]
diff --git a/tests/corpora/test_paratext_project_settings.py b/tests/corpora/test_paratext_project_settings.py
index d3fe5812..a4725801 100644
--- a/tests/corpora/test_paratext_project_settings.py
+++ b/tests/corpora/test_paratext_project_settings.py
@@ -113,6 +113,11 @@ def test_get_book_id_wrong_book_part_book_num_book_id() -> None:
     assert settings.get_book_id("PROJ100.SFM") is None
 
 
+def test_get_book_id_case_insensitive() -> None:
+    settings = _create_settings("MAT")
+    assert settings.get_book_id("PROJMRK.sfm") == "MRK"
+
+
 def _create_settings(file_name_form: str) -> ParatextProjectSettings:
     return ParatextProjectSettings(
         "id",