diff --git a/src/include/lwip/errno.h b/src/include/lwip/errno.h
index 641cffb0..20e43759 100644
--- a/src/include/lwip/errno.h
+++ b/src/include/lwip/errno.h
@@ -43,7 +43,7 @@
 extern "C" {
 #endif
 
-#ifdef LWIP_PROVIDE_ERRNO
+#if LWIP_PROVIDE_ERRNO
 
 #define  EPERM            1  /* Operation not permitted */
 #define  ENOENT           2  /* No such file or directory */