diff --git a/system/cu/cu_main.c b/system/cu/cu_main.c
index c909d3014..0d70cf3a7 100644
--- a/system/cu/cu_main.c
+++ b/system/cu/cu_main.c
@@ -61,6 +61,14 @@
  * Pre-processor Definitions
  ****************************************************************************/
 
+#ifndef SIGKILL
+#  define SIGKILL 9
+#endif
+
+/****************************************************************************
+ * Private Types
+ ****************************************************************************/
+
 enum parity_mode
 {
   PARITY_NONE,