diff --git a/include/dot11.h b/include/dot11.h
index f1dabce..790d2f8 100644
--- a/include/dot11.h
+++ b/include/dot11.h
@@ -2689,7 +2689,9 @@ namespace Tins {
 
         uint32_t write_ext_header(uint8_t *buffer, uint32_t total_sz);
 
-        uint32_t data_frame_size() { return sizeof(_ext_header) + (from_ds() && to_ds()) ? sizeof(_addr4) : 0; }
+        uint32_t data_frame_size() { 
+            return sizeof(_ext_header) + ((from_ds() && to_ds()) ? sizeof(_addr4) : 0); 
+        }
     private:
         ExtendedHeader _ext_header;
         address_type _addr4;