diff --git a/configure.ac b/configure.ac
index cd8ae615..3c86a21a 100644
--- a/configure.ac
+++ b/configure.ac
@@ -41,6 +41,9 @@ case "$host" in
 	;;
     *hpux*)
     ;;
+    *osf*)
+    CFLAGS="$CFLAGS -D_POSIX_PII_SOCKET"
+    ;;
     *)
     ;;
 esac