--- sfkbase.hpp
+++ sfkbase.hpp
@@ -7,9 +7,15 @@
 // ========== core includes and operating system abstraction ==========
 
 // enable LFS esp. on linux:
+#ifndef _LARGEFILE_SOURCE
 #define _LARGEFILE_SOURCE
+#endif
+#ifndef _LARGEFILE64_SOURCE
 #define _LARGEFILE64_SOURCE
+#endif
+#ifndef _FILE_OFFSET_BITS
 #define _FILE_OFFSET_BITS 64
+#endif
 
 #ifdef _WIN32
  #define WINFULL