diff --git a/lib/append.c b/lib/append.c
index 13e1ace..e8bd89d 100644
--- a/lib/append.c
+++ b/lib/append.c
@@ -13,6 +13,8 @@
 #include <internal.h>
 
 #include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
 #include <errno.h>
 #include <fcntl.h>
 #include <sys/param.h>
diff --git a/lib/output.c b/lib/output.c
index a2db929..a5262ee 100644
--- a/lib/output.c
+++ b/lib/output.c
@@ -13,6 +13,7 @@
 #include <internal.h>
 
 #include <stdio.h>
+#include <stdlib.h>
 #include <pwd.h>
 #include <grp.h>
 #include <time.h>
diff --git a/lib/wrapper.c b/lib/wrapper.c
index 4cd0652..44cc435 100644
--- a/lib/wrapper.c
+++ b/lib/wrapper.c
@@ -13,6 +13,7 @@
 #include <internal.h>
 
 #include <stdio.h>
+#include <stdlib.h>
 #include <sys/param.h>
 #include <dirent.h>
 #include <errno.h>