diff --git a/src/include/lwipopts.h b/src/include/lwipopts.h
index 5ba123f..baf739e 100644
--- a/src/include/lwipopts.h
+++ b/src/include/lwipopts.h
@@ -244,9 +244,13 @@
 
 #define SO_REUSE 1
 
+#ifndef FIONBIO
 #define FIONBIO 0x5421 /* same as define in asm-generic/ioctls.h */
+#endif
 
+#ifndef O_NONBLOCK
 #define O_NONBLOCK 04000 /* same as define in bits/fcntl-linux.h */
+#endif
 
 #define SIOCSHIWAT 1