diff --git a/libc/stdio/lib_sscanf.c b/libc/stdio/lib_sscanf.c
index 611a0edc0c..adad401352 100644
--- a/libc/stdio/lib_sscanf.c
+++ b/libc/stdio/lib_sscanf.c
@@ -430,6 +430,7 @@ int vsscanf(FAR const char *buf, FAR const char *fmt, va_list ap)
                       base = 10;
                       break;
 
+                    case 'X':
                     case 'x':
                       base = 16;
                       break;