diff --git a/CHANGES b/CHANGES
index c465073..63945da 100644
--- a/CHANGES
+++ b/CHANGES
@@ -37,6 +37,10 @@ porting:
 	DTLSv1_client_method or DTLSv1_server_method.
 	Thanks to Simon Matter for sending a patch.
 
+	NuttX OS headers do not provide struct ip, thus socat did not compile.
+	Made struct ip subject to configure.
+	Thanks to SP for reporting this issue.
+
 testing:
 	socks4echo.sh and socks4a-echo.sh hung with new bash with read -n
 
diff --git a/config.h.in b/config.h.in
index 414379b..a3be40d 100644
--- a/config.h.in
+++ b/config.h.in
@@ -359,6 +359,9 @@
 /* Define if you have struct linger */
 #undef HAVE_STRUCT_LINGER
 
+/* Define if you have struct ip */
+#undef HAVE_STRUCT_IP
+
 /* Define if you have struct ip_mreq */
 #undef HAVE_STRUCT_IP_MREQ
 
diff --git a/configure.in b/configure.in
index 6db8709..0c8d5fa 100644
--- a/configure.in
+++ b/configure.in
@@ -1118,6 +1118,17 @@ fi
 AC_MSG_RESULT($sc_cv_struct_linger)
 
 
+# struct ip (for IPv4 header info)
+AC_MSG_CHECKING(for struct ip)
+AC_CACHE_VAL(sc_cv_struct_ip,
+[AC_TRY_COMPILE([#include <netinet/ip.h>],[struct ip s;],
+[sc_cv_struct_ip=yes],
+[sc_cv_struct_ip=no])])
+if test $sc_cv_struct_ip = yes; then
+   AC_DEFINE(HAVE_STRUCT_IP)
+fi
+AC_MSG_RESULT($sc_cv_struct_ip)
+
 # struct ip_mreq (for multicasting options)
 AC_MSG_CHECKING(for struct ip_mreq)
 AC_CACHE_VAL(sc_cv_struct_ip_mreq,
diff --git a/xioread.c b/xioread.c
index f4dd8e6..24f3c88 100644
--- a/xioread.c
+++ b/xioread.c
@@ -221,9 +221,12 @@ ssize_t xioread(xiofile_t *file, void *buff, size_t bufsiz) {
       }
 
       switch(from.soa.sa_family) {
+#if HAVE_STRUCT_IP
 	 int headlen;
+#endif /* HAVE_STRUCT_IP */
 #if WITH_IP4
       case AF_INET:
+#if HAVE_STRUCT_IP
 	 if (pipe->dtype & XIOREAD_RECV_SKIPIP) {
 	    /* IP4 raw sockets include the header when passing a packet to the
 	       application - we don't need it here. */
@@ -240,6 +243,7 @@ ssize_t xioread(xiofile_t *file, void *buff, size_t bufsiz) {
 	       bytes -= headlen;
 	    }
 	 }
+#endif /* HAVE_STRUCT_IP */
 	 break;
 #endif
 #if WITH_IP6
@@ -357,9 +361,12 @@ ssize_t xioread(xiofile_t *file, void *buff, size_t bufsiz) {
       }
 
       switch(from.soa.sa_family) {
+#if HAVE_STRUCT_IP
 	 int headlen;
+#endif /* HAVE_STRUCT_IP */
 #if WITH_IP4
       case AF_INET:
+#if HAVE_STRUCT_IP
 	 if (pipe->dtype & XIOREAD_RECV_SKIPIP) {
 	    /* IP4 raw sockets include the header when passing a packet to the
 	       application - we don't need it here. */
@@ -376,6 +383,7 @@ ssize_t xioread(xiofile_t *file, void *buff, size_t bufsiz) {
 	       bytes -= headlen;
 	    }
 	 }
+#endif /* HAVE_STRUCT_IP */
 	 break;
 #endif
 #if WITH_IP6