diff --git a/frappe/core/doctype/file/file.py b/frappe/core/doctype/file/file.py
index af3d835452..2ded1fe3a5 100755
--- a/frappe/core/doctype/file/file.py
+++ b/frappe/core/doctype/file/file.py
@@ -336,7 +336,7 @@ class File(Document):
 		if self.is_folder:
 			return
 
-		file_type = mimetypes.guess_type(self.file_name)[0]
+		file_type = mimetypes.guess_type(self.file_url)[0]
 		if not file_type:
 			return
 
diff --git a/frappe/patches/v15_0/set_file_type.py b/frappe/patches/v15_0/set_file_type.py
index 9805b1d39c..cf2d507a5c 100644
--- a/frappe/patches/v15_0/set_file_type.py
+++ b/frappe/patches/v15_0/set_file_type.py
@@ -7,26 +7,28 @@ def execute():
 	"""Set 'File Type' for all files based on file extension."""
 	files = frappe.db.get_all(
 		"File",
-		fields=["name", "file_name", "is_folder"],
+		fields=["name", "file_url"],
+		filters={
+			"is_folder": 0,
+			"file_type": ("is", "not set")
+		},
 	)
 
 	frappe.db.auto_commit_on_many_writes = 1
 
 	for file in files:
-		if file.get("is_folder"):
-			continue
-
-		file_extension = get_file_extension(file.get("file_name"))
+		# File URL could be relative to site's public folder or a web URL
+		file_extension = get_file_extension(file.file_url)
 		if file_extension:
 			frappe.db.set_value(
-				"File", file.get("name"), "file_type", file_extension, update_modified=False
+				"File", file.name, "file_type", file_extension, update_modified=False
 			)
 
 	frappe.db.auto_commit_on_many_writes = 0
 
 
-def get_file_extension(file_name):
-	file_type = mimetypes.guess_type(file_name)[0]
+def get_file_extension(file_url):
+	file_type = mimetypes.guess_type(file_url)[0]
 	if not file_type:
 		return None