--- a/src/op-mp.h
+++ b/src/op-mp.h
@@ -20,8 +20,11 @@
 #if !defined (op_mp_h)
 #define op_mp_h 1
 
+#include <octave/ops.h>
+
 #include "ov-mp.h"
-#include <octave/ops.h>
+
+void install_mp_ops();
 
 DEFNCUNOP_METHOD (s_incr, mp, increment)
 DEFNCUNOP_METHOD (s_decr, mp, decrement)