diff --git a/src/s/irix6-0.h b/src/s/irix6-0.h
index 31adffd55d3..be50494c6d7 100644
--- a/src/s/irix6-0.h
+++ b/src/s/irix6-0.h
@@ -23,3 +23,6 @@
 #endif
 
 #undef SA_RESTART
+
+/* Canced the #define that is in irix5-0.h.  */
+#undef ospeed