diff --git a/rdr/FdInStream.cxx b/rdr/FdInStream.cxx
index f64f68e..2b11973 100644
--- a/rdr/FdInStream.cxx
+++ b/rdr/FdInStream.cxx
@@ -48,6 +48,11 @@
 #include <sys/select.h>
 #endif
 
+// XXX Lynx/OS 2.3: protos for gettimeofday(), select(), bzero()
+#ifdef Lynx
+#include <sys/proto.h>
+#endif
+
 #include <rdr/FdInStream.h>
 #include <rdr/Exception.h>
 
diff --git a/rdr/FdOutStream.cxx b/rdr/FdOutStream.cxx
index e65133d..07ac04c 100644
--- a/rdr/FdOutStream.cxx
+++ b/rdr/FdOutStream.cxx
@@ -33,6 +33,11 @@
 #include <sys/time.h>
 #endif
 
+// XXX Lynx/OS 2.3: protos for select(), bzero()
+#ifdef Lynx
+#include <sys/proto.h>
+#endif
+
 #include <rdr/FdOutStream.h>
 #include <rdr/Exception.h>