diff --git a/lang/occam/comp/expr.c b/lang/occam/comp/expr.c
index 1f2719cb3..36eef9c0e 100644
--- a/lang/occam/comp/expr.c
+++ b/lang/occam/comp/expr.c
@@ -3,6 +3,7 @@
  * (c) copyright 1987 by the Vrije Universiteit, Amsterdam, The Netherlands.
  * See the copyright notice in the ACK home directory, in the file "Copyright".
  */
+#include <stdio.h>
 #include "symtab.h"
 #include "sizes.h"
 #include "expr.h"