diff --git a/configure.in b/configure.in
index fbd436b..6f99ae9 100644
--- a/configure.in
+++ b/configure.in
@@ -50,6 +50,10 @@
 # them.
 AC_DEFINE(__BSD_VISIBLE, 1, [Define on FreeBSD to activate all library features])
 
+# The later defininition of _XOPEN_SOURCE and _POSIX_C_SOURCE disables
+# u_int on Irix 5.3. Defining _BSD_TYPES brings it back.
+AC_DEFINE(_BSD_TYPES, 1, [Define on Irix to enable u_int])
+
 define_xopen_source=yes
 
 # Arguments passed to configure.