--- a/runtime/comerror.c
+++ b/runtime/comerror.c
@@ -22,6 +22,7 @@
 #include <caml/callback.h>
 #include <caml/fail.h>
 #include <caml/alloc.h>
+#include <caml/printexc.h>
 #include "camlidlruntime.h"
 #include "comstuff.h"