diff --git a/doomgeneric/doomgeneric.h b/doomgeneric/doomgeneric.h
index 2588710..c2dc4b5 100644
--- a/doomgeneric/doomgeneric.h
+++ b/doomgeneric/doomgeneric.h
@@ -1,6 +1,7 @@
 #ifndef DOOM_GENERIC
 #define DOOM_GENERIC
 
+#include <stdlib.h>
 #include <stdint.h>
 
 #define DOOMGENERIC_RESX 640
diff --git a/doomgeneric/doomgeneric_xlib.c b/doomgeneric/doomgeneric_xlib.c
index cf92fc7..f6d6a31 100644
--- a/doomgeneric/doomgeneric_xlib.c
+++ b/doomgeneric/doomgeneric_xlib.c
@@ -2,6 +2,7 @@
 
 #include "doomgeneric.h"
 
+#include <ctype.h>
 #include <stdio.h>
 #include <string.h>
 #include <unistd.h>