diff --git a/SWIG/Lib/ocaml/director.swg b/SWIG/Lib/ocaml/director.swg
index 045cb12d8..282fc147c 100644
--- a/SWIG/Lib/ocaml/director.swg
+++ b/SWIG/Lib/ocaml/director.swg
@@ -11,6 +11,7 @@
 
 %insert(runtime) %{
 
+#include <assert.h>
 #ifdef __cplusplus
 
 #include <string>