diff --git a/unix/mpconfigport_minimal.h b/unix/mpconfigport_minimal.h
index 15a5f7d852..65e35c8d99 100644
--- a/unix/mpconfigport_minimal.h
+++ b/unix/mpconfigport_minimal.h
@@ -40,6 +40,7 @@
 #define MICROPY_COMP_CONST          (0)
 #define MICROPY_MEM_STATS           (0)
 #define MICROPY_DEBUG_PRINTERS      (0)
+#define MICROPY_READER_POSIX        (1)
 #define MICROPY_HELPER_REPL         (1)
 #define MICROPY_HELPER_LEXER_UNIX   (1)
 #define MICROPY_ENABLE_SOURCE_LINE  (0)