diff --git a/CHANGELOG.md b/CHANGELOG.md
index 633d75d..baadf98 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,13 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 
 ## [Unreleased]
 
+When upgrading to this version, `ALLOWED_UNKNOWN_CONTENT_TYPES` must be set in the Django settings file, ideally from the settings file included with this library.
+
+## Added
+
+- utils.py: get_file_type_for_flatten_tool: consider content type too
+- settings.ALLOWED_UNKNOWN_CONTENT_TYPES.
+
 ## Fixed
 
 - utils.py: get_file_type_for_flatten_tool: include an error message in raise at end https://github.com/OpenDataServices/lib-cove-web-2/issues/3
diff --git a/libcoveweb2/settings.py b/libcoveweb2/settings.py
index 2145264..8938158 100644
--- a/libcoveweb2/settings.py
+++ b/libcoveweb2/settings.py
@@ -173,21 +173,29 @@
     },
 }
 
-ALLOWED_JSON_CONTENT_TYPES = ["application/json", "application/octet-stream"]
+# Sometimes uploads happen with a generic content type.
+# In this case, we can't rely on content type to detect type.
+# But the type is still allowed, so it's added to
+#   ALLOWED_*_CONTENT_TYPES when they are defined.
+ALLOWED_UNKNOWN_CONTENT_TYPES = ["application/octet-stream"]
+
+# JSON details
+ALLOWED_JSON_CONTENT_TYPES = ["application/json"] + ALLOWED_UNKNOWN_CONTENT_TYPES
 ALLOWED_JSON_EXTENSIONS = [".json"]
 
+# Excel details
 ALLOWED_SPREADSHEET_EXCEL_CONTENT_TYPES = [
     "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet",
-    "application/octet-stream",
-]
+] + ALLOWED_UNKNOWN_CONTENT_TYPES
 ALLOWED_SPREADSHEET_EXCEL_EXTENSIONS = [".xlsx"]
 
+# Open Document details
 ALLOWED_SPREADSHEET_OPENDOCUMENT_CONTENT_TYPES = [
     "application/vnd.oasis.opendocument.spreadsheet",
-    "application/octet-stream",
-]
+] + ALLOWED_UNKNOWN_CONTENT_TYPES
 ALLOWED_SPREADSHEET_OPENDOCUMENT_EXTENSIONS = [".ods"]
 
+# Spreadsheet details (sum of details above)
 ALLOWED_SPREADSHEET_CONTENT_TYPES = (
     ALLOWED_SPREADSHEET_EXCEL_CONTENT_TYPES
     + ALLOWED_SPREADSHEET_OPENDOCUMENT_CONTENT_TYPES
@@ -196,5 +204,6 @@
     ALLOWED_SPREADSHEET_EXCEL_EXTENSIONS + ALLOWED_SPREADSHEET_OPENDOCUMENT_EXTENSIONS
 )
 
-ALLOWED_CSV_CONTENT_TYPES = ["text/csv", "application/octet-stream"]
+# CSV Details
+ALLOWED_CSV_CONTENT_TYPES = ["text/csv"] + ALLOWED_UNKNOWN_CONTENT_TYPES
 ALLOWED_CSV_EXTENSIONS = [".csv"]
diff --git a/libcoveweb2/utils.py b/libcoveweb2/utils.py
index 1379b02..efe6e53 100644
--- a/libcoveweb2/utils.py
+++ b/libcoveweb2/utils.py
@@ -29,6 +29,26 @@ def get_file_type_for_flatten_tool(supplied_data_file: SuppliedDataFile):
     for extension in settings.ALLOWED_CSV_EXTENSIONS:
         if supplied_data_file.filename.lower().endswith(extension):
             return "csv"
+    # Check the content type
+    if (
+        supplied_data_file.content_type
+        and supplied_data_file.content_type
+        not in settings.ALLOWED_UNKNOWN_CONTENT_TYPES
+    ):
+        if supplied_data_file.content_type in settings.ALLOWED_JSON_CONTENT_TYPES:
+            return "json"
+        if (
+            supplied_data_file.content_type
+            in settings.ALLOWED_SPREADSHEET_EXCEL_CONTENT_TYPES
+        ):
+            return "xlsx"
+        if (
+            supplied_data_file.content_type
+            in settings.ALLOWED_SPREADSHEET_OPENDOCUMENT_CONTENT_TYPES
+        ):
+            return "ods"
+        if supplied_data_file.content_type in settings.ALLOWED_CSV_CONTENT_TYPES:
+            return "csv"
     # Try and load the first bit of the file to see if it's JSON?
     try:
         with open(supplied_data_file.upload_dir_and_filename(), "rb") as fp: