diff --git a/main.go b/main.go
index 78c8271..a7a0b01 100755
--- a/main.go
+++ b/main.go
@@ -154,7 +154,9 @@ func main() {
 			mimeType := "application/octet-stream"
 			extPos := strings.LastIndex(info.Name(), ".")
 			if extPos != -1 {
-				mimeType = mime.TypeByExtension(info.Name()[:extPos])
+				if m := mime.TypeByExtension(info.Name()[extPos:]); m != "" {
+					mimeType = m
+				}
 			}
 
 			w.Header().Set("Content-Type", mimeType)