diff --git a/components/libc/minilibc/sys/types.h b/components/libc/minilibc/sys/types.h
index 27967cd6af..6d92d80826 100644
--- a/components/libc/minilibc/sys/types.h
+++ b/components/libc/minilibc/sys/types.h
@@ -22,4 +22,6 @@ typedef int pid_t;
 #define NULL RT_NULL
 #endif
 
+#define __u_char_defined
+
 #endif