diff --git a/src/drivers/libretro/libretro.c b/src/drivers/libretro/libretro.c
index 02dc738..5aa8526 100644
--- a/src/drivers/libretro/libretro.c
+++ b/src/drivers/libretro/libretro.c
@@ -3,6 +3,7 @@
 #include <stdlib.h>
 #include <string.h>
 #include <stdarg.h>
+#include <ctype.h>
 
 #include <libretro.h>
 #include <streams/memory_stream.h>