--- a/Group.c
+++ b/Group.c
@@ -20,6 +20,7 @@
 */
 
 // standard
+#include <cstdlib>
 #include <sys/types.h>                          /* needed by FreeBSD systems */
 #include <grp.h>                                /* for getgrnam(3) */
 
--- a/IncludeMeta.c
+++ b/IncludeMeta.c
@@ -20,6 +20,7 @@
 */
 
 // standard
+#include <cstdlib>
 #include <cstring>
 
 // local
--- a/User.c
+++ b/User.c
@@ -20,6 +20,7 @@
 */
 
 // standard
+#include <cstdlib>
 #include <pwd.h>                                /* for getpwnam(3) */
 
 // local
--- a/WordThreshold.c
+++ b/WordThreshold.c
@@ -20,6 +20,7 @@
 */
 
 // standard
+#include <cstdlib>
 #include <sys/types.h>                          /* needed by FreeBSD systems */
 #include <unistd.h>                             /* for geteuid(2) */
 
--- a/conf_bool.c
+++ b/conf_bool.c
@@ -20,6 +20,7 @@
 */
 
 // standard
+#include <cstdlib>
 #include <iostream>
 
 // local
--- a/conf_enum.c
+++ b/conf_enum.c
@@ -20,6 +20,7 @@
 */
 
 // standard
+#include <cstdlib>
 #include <iostream>
 
 // local
--- a/conf_percent.c
+++ b/conf_percent.c
@@ -20,6 +20,7 @@
 */
 
 // standard
+#include <cstdlib>
 #include <cstring>
 
 // local
--- a/conf_string.c
+++ b/conf_string.c
@@ -20,6 +20,7 @@
 */
 
 // standard
+#include <cstdlib>
 #include <cstring>
 #include <iostream>
 
--- a/conf_var.c
+++ b/conf_var.c
@@ -21,6 +21,7 @@
 
 // standard
 #include <cctype>
+#include <cstdlib>
 #include <cstring>
 #include <iostream>
 
--- a/mod/html/mod_html.c
+++ b/mod/html/mod_html.c
@@ -23,6 +23,7 @@
 
 // standard
 #include <cctype>
+#include <cstdlib>
 #include <cstring>
 #include <utility>                              /* for pair<> */
 #include <vector>
--- a/stop_words.c
+++ b/stop_words.c
@@ -21,6 +21,7 @@
 
 // standard
 #include <cctype>
+#include <cstdlib>
 
 // local
 #include "config.h"
