diff --git a/server_test.go b/server_test.go
index a590465..6fe363c 100644
--- a/server_test.go
+++ b/server_test.go
@@ -699,7 +699,7 @@ func TestPutUpload(t *testing.T) {
 	mux := setup()
 	w := httptest.NewRecorder()
 
-	filename := generateBarename() + ".ext"
+	filename := generateBarename() + ".file"
 
 	req, err := http.NewRequest("PUT", "/upload/"+filename, strings.NewReader("File content"))
 	if err != nil {
@@ -717,7 +717,7 @@ func TestPutRandomizedUpload(t *testing.T) {
 	mux := setup()
 	w := httptest.NewRecorder()
 
-	filename := generateBarename() + ".ext"
+	filename := generateBarename() + ".file"
 
 	req, err := http.NewRequest("PUT", "/upload/"+filename, strings.NewReader("File content"))
 	if err != nil {
@@ -757,7 +757,7 @@ func TestPutEmptyUpload(t *testing.T) {
 	mux := setup()
 	w := httptest.NewRecorder()
 
-	filename := generateBarename() + ".ext"
+	filename := generateBarename() + ".file"
 
 	req, err := http.NewRequest("PUT", "/upload/"+filename, strings.NewReader(""))
 	if err != nil {
@@ -779,7 +779,7 @@ func TestPutJSONUpload(t *testing.T) {
 	mux := setup()
 	w := httptest.NewRecorder()
 
-	filename := generateBarename() + ".ext"
+	filename := generateBarename() + ".file"
 
 	req, err := http.NewRequest("PUT", "/upload/"+filename, strings.NewReader("File content"))
 	if err != nil {
@@ -806,7 +806,7 @@ func TestPutRandomizedJSONUpload(t *testing.T) {
 	mux := setup()
 	w := httptest.NewRecorder()
 
-	filename := generateBarename() + ".ext"
+	filename := generateBarename() + ".file"
 
 	req, err := http.NewRequest("PUT", "/upload/"+filename, strings.NewReader("File content"))
 	if err != nil {
@@ -834,7 +834,7 @@ func TestPutExpireJSONUpload(t *testing.T) {
 	mux := setup()
 	w := httptest.NewRecorder()
 
-	filename := generateBarename() + ".ext"
+	filename := generateBarename() + ".file"
 
 	req, err := http.NewRequest("PUT", "/upload/"+filename, strings.NewReader("File content"))
 	if err != nil {
diff --git a/upload.go b/upload.go
index bd2bed6..9cf8713 100644
--- a/upload.go
+++ b/upload.go
@@ -219,11 +219,11 @@ func processUpload(upReq UploadRequest) (upload Upload, err error) {
 
 		// Determine the type of file from header
 		kind, err := filetype.Match(header)
-		if err != nil {
-			extension = "ext"
+		if err != nil || kind.Extension == "unknown" {
+			extension = "file"
+		} else {
+			extension = kind.Extension
 		}
-
-		extension = kind.Extension
 	}
 
 	upload.Filename = strings.Join([]string{barename, extension}, ".")