diff --git a/windows/mpconfigport.h b/windows/mpconfigport.h
index 88596977cf..6156ad39ef 100644
--- a/windows/mpconfigport.h
+++ b/windows/mpconfigport.h
@@ -43,6 +43,7 @@
 #define MICROPY_MALLOC_USES_ALLOCATED_SIZE (1)
 #define MICROPY_MEM_STATS           (1)
 #define MICROPY_DEBUG_PRINTERS      (1)
+#define MICROPY_READER_POSIX        (1)
 #define MICROPY_USE_READLINE_HISTORY (1)
 #define MICROPY_HELPER_REPL         (1)
 #define MICROPY_REPL_EMACS_KEYS     (1)