diff --git a/py/mpconfig.h b/py/mpconfig.h
index 42ef19b72c..aaf1bc6125 100644
--- a/py/mpconfig.h
+++ b/py/mpconfig.h
@@ -555,6 +555,11 @@ typedef double mp_float_t;
 #define MICROPY_BUILTIN_METHOD_CHECK_SELF_ARG (1)
 #endif
 
+// Whether to use internally defined errno's (otherwise system provided ones)
+#ifndef MICROPY_USE_INTERNAL_ERRNO
+#define MICROPY_USE_INTERNAL_ERRNO (0)
+#endif
+
 // Support for user-space VFS mount (selected ports)
 #ifndef MICROPY_FSUSERMOUNT
 #define MICROPY_FSUSERMOUNT (0)
diff --git a/py/mperrno.h b/py/mperrno.h
new file mode 100644
index 0000000000..89649446c5
--- /dev/null
+++ b/py/mperrno.h
@@ -0,0 +1,117 @@
+/*
+ * This file is part of the MicroPython project, http://micropython.org/
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2016 Damien P. George
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#ifndef __MICROPY_INCLUDED_PY_MPERRNO_H__
+#define __MICROPY_INCLUDED_PY_MPERRNO_H__
+
+#if MICROPY_USE_INTERNAL_ERRNO
+
+// MP_Exxx errno's are defined directly as numeric values
+// (Linux constants are used as a reference)
+
+#define MP_EPERM              (1) // Operation not permitted
+#define MP_ENOENT             (2) // No such file or directory
+#define MP_ESRCH              (3) // No such process
+#define MP_EINTR              (4) // Interrupted system call
+#define MP_EIO                (5) // I/O error
+#define MP_ENXIO              (6) // No such device or address
+#define MP_E2BIG              (7) // Argument list too long
+#define MP_ENOEXEC            (8) // Exec format error
+#define MP_EBADF              (9) // Bad file number
+#define MP_ECHILD            (10) // No child processes
+#define MP_EAGAIN            (11) // Try again
+#define MP_ENOMEM            (12) // Out of memory
+#define MP_EACCES            (13) // Permission denied
+#define MP_EFAULT            (14) // Bad address
+#define MP_ENOTBLK           (15) // Block device required
+#define MP_EBUSY             (16) // Device or resource busy
+#define MP_EEXIST            (17) // File exists
+#define MP_EXDEV             (18) // Cross-device link
+#define MP_ENODEV            (19) // No such device
+#define MP_ENOTDIR           (20) // Not a directory
+#define MP_EISDIR            (21) // Is a directory
+#define MP_EINVAL            (22) // Invalid argument
+#define MP_ENFILE            (23) // File table overflow
+#define MP_EMFILE            (24) // Too many open files
+#define MP_ENOTTY            (25) // Not a typewriter
+#define MP_ETXTBSY           (26) // Text file busy
+#define MP_EFBIG             (27) // File too large
+#define MP_ENOSPC            (28) // No space left on device
+#define MP_ESPIPE            (29) // Illegal seek
+#define MP_EROFS             (30) // Read-only file system
+#define MP_EMLINK            (31) // Too many links
+#define MP_EPIPE             (32) // Broken pipe
+#define MP_EDOM              (33) // Math argument out of domain of func
+#define MP_ERANGE            (34) // Math result not representable
+#define MP_ENOTCONN         (107) // Transport endpoint is not connected
+#define MP_ETIMEDOUT        (110) // Connection timed out
+
+#else
+
+// MP_Exxx errno's are defined in terms of system supplied ones
+
+#include <errno.h>
+
+#define MP_EPERM            EPERM
+#define MP_ENOENT           ENOENT
+#define MP_ESRCH            ESRCH
+#define MP_EINTR            EINTR
+#define MP_EIO              EIO
+#define MP_ENXIO            ENXIO
+#define MP_E2BIG            E2BIG
+#define MP_ENOEXEC          ENOEXEC
+#define MP_EBADF            EBADF
+#define MP_ECHILD           ECHILD
+#define MP_EAGAIN           EAGAIN
+#define MP_ENOMEM           ENOMEM
+#define MP_EACCES           EACCES
+#define MP_EFAULT           EFAULT
+#define MP_ENOTBLK          ENOTBLK
+#define MP_EBUSY            EBUSY
+#define MP_EEXIST           EEXIST
+#define MP_EXDEV            EXDEV
+#define MP_ENODEV           ENODEV
+#define MP_ENOTDIR          ENOTDIR
+#define MP_EISDIR           EISDIR
+#define MP_EINVAL           EINVAL
+#define MP_ENFILE           ENFILE
+#define MP_EMFILE           EMFILE
+#define MP_ENOTTY           ENOTTY
+#define MP_ETXTBSY          ETXTBSY
+#define MP_EFBIG            EFBIG
+#define MP_ENOSPC           ENOSPC
+#define MP_ESPIPE           ESPIPE
+#define MP_EROFS            EROFS
+#define MP_EMLINK           EMLINK
+#define MP_EPIPE            EPIPE
+#define MP_EDOM             EDOM
+#define MP_ERANGE           ERANGE
+#define MP_ENOTCONN         ENOTCONN
+#define MP_ETIMEDOUT        ETIMEDOUT
+
+#endif
+
+#endif // __MICROPY_INCLUDED_PY_MPERRNO_H__