diff --git a/lang/occam/comp/em.c b/lang/occam/comp/em.c
index 9e39ae005..ecd779824 100644
--- a/lang/occam/comp/em.c
+++ b/lang/occam/comp/em.c
@@ -3,10 +3,13 @@
  * (c) copyright 1987 by the Vrije Universiteit, Amsterdam, The Netherlands.
  * See the copyright notice in the ACK home directory, in the file "Copyright".
  */
+
+#include <stdlib.h>
+#include <string.h>
 #include "sizes.h"
 #include "Lpars.h"
-#include <em.h>
 #include "em.h"
+#include "occam-em.h"
 
 /* This file is used to shield code.c as much as possible from em dependant
  * details.  It introduces some call overhead but not enough for a coffee
diff --git a/lang/occam/comp/occam.g b/lang/occam/comp/occam.g
index cfa7216c2..3385cca32 100644
--- a/lang/occam/comp/occam.g
+++ b/lang/occam/comp/occam.g
@@ -5,6 +5,7 @@
  */
 /*	OCCAM		*/
 {
+#include <stdlib.h>
 #include "token.h"
 #include "symtab.h"
 #include "expr.h"
diff --git a/lang/occam/comp/report.c b/lang/occam/comp/report.c
index c2e639019..62f2b5fe3 100644
--- a/lang/occam/comp/report.c
+++ b/lang/occam/comp/report.c
@@ -3,6 +3,8 @@
  * (c) copyright 1987 by the Vrije Universiteit, Amsterdam, The Netherlands.
  * See the copyright notice in the ACK home directory, in the file "Copyright".
  */
+
+#include <stdlib.h>
 #include <system.h>
 
 extern int err, lineno;
diff --git a/modules/src/em_code/C_out.c b/modules/src/em_code/C_out.c
index 1986ea452..135934096 100644
--- a/modules/src/em_code/C_out.c
+++ b/modules/src/em_code/C_out.c
@@ -1,3 +1,4 @@
+#include <stdlib.h>
 #include "em_arith.h"
 #include "em_label.h"
 #include "../read_em/em_comp.h"
diff --git a/util/ack/scan.c b/util/ack/scan.c
index abf8313e5..c4388b152 100644
--- a/util/ack/scan.c
+++ b/util/ack/scan.c
@@ -4,6 +4,8 @@
  *
  */
 
+#include <stdlib.h>
+#include <string.h>
 #include "ack.h"
 #include "list.h"
 #include "trans.h"