diff --git a/src/api/err.c b/src/api/err.c
index 1593e70..35e9c02 100644
--- a/src/api/err.c
+++ b/src/api/err.c
@@ -64,6 +64,15 @@
   ENOTCONN,      /* ERR_CLSD       -15     Connection closed.       */
   EIO            /* ERR_ARG        -16     Illegal argument.        */
 };
+
+int
+err_to_errno(err_t err)
+{
+  if ((err > 0) || (-err >= (err_t)LWIP_ARRAYSIZE(err_to_errno_table))) {
+    return EIO;
+  }
+  return err_to_errno_table[-err];
+}
 #endif /* !NO_SYS */
 
 #ifdef LWIP_DEBUG
@@ -104,14 +113,3 @@
 }
 
 #endif /* LWIP_DEBUG */
-
-#if !NO_SYS
-int
-err_to_errno(err_t err)
-{
-  if ((err > 0) || (-err >= (err_t)LWIP_ARRAYSIZE(err_to_errno_table))) {
-    return EIO;
-  }
-  return err_to_errno_table[-err];
-}
-#endif /* !NO_SYS */
diff --git a/src/include/lwip/errno.h b/src/include/lwip/errno.h
index 25bc1f8..641cffb 100644
--- a/src/include/lwip/errno.h
+++ b/src/include/lwip/errno.h
@@ -45,100 +45,100 @@
 
 #ifdef LWIP_PROVIDE_ERRNO
 
-#define  EPERM         1  /* Operation not permitted */
-#define  ENOENT        2  /* No such file or directory */
-#define  ESRCH         3  /* No such process */
-#define  EINTR         4  /* Interrupted system call */
-#define  EIO           5  /* I/O error */
-#define  ENXIO         6  /* No such device or address */
-#define  E2BIG         7  /* Arg list too long */
-#define  ENOEXEC       8  /* Exec format error */
-#define  EBADF         9  /* Bad file number */
-#define  ECHILD       10  /* No child processes */
-#define  EAGAIN       11  /* Try again */
-#define  ENOMEM       12  /* Out of memory */
-#define  EACCES       13  /* Permission denied */
-#define  EFAULT       14  /* Bad address */
-#define  ENOTBLK      15  /* Block device required */
-#define  EBUSY        16  /* Device or resource busy */
-#define  EEXIST       17  /* File exists */
-#define  EXDEV        18  /* Cross-device link */
-#define  ENODEV       19  /* No such device */
-#define  ENOTDIR      20  /* Not a directory */
-#define  EISDIR       21  /* Is a directory */
-#define  EINVAL       22  /* Invalid argument */
-#define  ENFILE       23  /* File table overflow */
-#define  EMFILE       24  /* Too many open files */
-#define  ENOTTY       25  /* Not a typewriter */
-#define  ETXTBSY      26  /* Text file busy */
-#define  EFBIG        27  /* File too large */
-#define  ENOSPC       28  /* No space left on device */
-#define  ESPIPE       29  /* Illegal seek */
-#define  EROFS        30  /* Read-only file system */
-#define  EMLINK       31  /* Too many links */
-#define  EPIPE        32  /* Broken pipe */
-#define  EDOM         33  /* Math argument out of domain of func */
-#define  ERANGE       34  /* Math result not representable */
-#define  EDEADLK      35  /* Resource deadlock would occur */
-#define  ENAMETOOLONG 36  /* File name too long */
-#define  ENOLCK       37  /* No record locks available */
-#define  ENOSYS       38  /* Function not implemented */
-#define  ENOTEMPTY    39  /* Directory not empty */
-#define  ELOOP        40  /* Too many symbolic links encountered */
-#define  EWOULDBLOCK  EAGAIN  /* Operation would block */
-#define  ENOMSG       42  /* No message of desired type */
-#define  EIDRM        43  /* Identifier removed */
-#define  ECHRNG       44  /* Channel number out of range */
-#define  EL2NSYNC     45  /* Level 2 not synchronized */
-#define  EL3HLT       46  /* Level 3 halted */
-#define  EL3RST       47  /* Level 3 reset */
-#define  ELNRNG       48  /* Link number out of range */
-#define  EUNATCH      49  /* Protocol driver not attached */
-#define  ENOCSI       50  /* No CSI structure available */
-#define  EL2HLT       51  /* Level 2 halted */
-#define  EBADE        52  /* Invalid exchange */
-#define  EBADR        53  /* Invalid request descriptor */
-#define  EXFULL       54  /* Exchange full */
-#define  ENOANO       55  /* No anode */
-#define  EBADRQC      56  /* Invalid request code */
-#define  EBADSLT      57  /* Invalid slot */
+#define  EPERM            1  /* Operation not permitted */
+#define  ENOENT           2  /* No such file or directory */
+#define  ESRCH            3  /* No such process */
+#define  EINTR            4  /* Interrupted system call */
+#define  EIO              5  /* I/O error */
+#define  ENXIO            6  /* No such device or address */
+#define  E2BIG            7  /* Arg list too long */
+#define  ENOEXEC          8  /* Exec format error */
+#define  EBADF            9  /* Bad file number */
+#define  ECHILD          10  /* No child processes */
+#define  EAGAIN          11  /* Try again */
+#define  ENOMEM          12  /* Out of memory */
+#define  EACCES          13  /* Permission denied */
+#define  EFAULT          14  /* Bad address */
+#define  ENOTBLK         15  /* Block device required */
+#define  EBUSY           16  /* Device or resource busy */
+#define  EEXIST          17  /* File exists */
+#define  EXDEV           18  /* Cross-device link */
+#define  ENODEV          19  /* No such device */
+#define  ENOTDIR         20  /* Not a directory */
+#define  EISDIR          21  /* Is a directory */
+#define  EINVAL          22  /* Invalid argument */
+#define  ENFILE          23  /* File table overflow */
+#define  EMFILE          24  /* Too many open files */
+#define  ENOTTY          25  /* Not a typewriter */
+#define  ETXTBSY         26  /* Text file busy */
+#define  EFBIG           27  /* File too large */
+#define  ENOSPC          28  /* No space left on device */
+#define  ESPIPE          29  /* Illegal seek */
+#define  EROFS           30  /* Read-only file system */
+#define  EMLINK          31  /* Too many links */
+#define  EPIPE           32  /* Broken pipe */
+#define  EDOM            33  /* Math argument out of domain of func */
+#define  ERANGE          34  /* Math result not representable */
+#define  EDEADLK         35  /* Resource deadlock would occur */
+#define  ENAMETOOLONG    36  /* File name too long */
+#define  ENOLCK          37  /* No record locks available */
+#define  ENOSYS          38  /* Function not implemented */
+#define  ENOTEMPTY       39  /* Directory not empty */
+#define  ELOOP           40  /* Too many symbolic links encountered */
+#define  EWOULDBLOCK     EAGAIN  /* Operation would block */
+#define  ENOMSG          42  /* No message of desired type */
+#define  EIDRM           43  /* Identifier removed */
+#define  ECHRNG          44  /* Channel number out of range */
+#define  EL2NSYNC        45  /* Level 2 not synchronized */
+#define  EL3HLT          46  /* Level 3 halted */
+#define  EL3RST          47  /* Level 3 reset */
+#define  ELNRNG          48  /* Link number out of range */
+#define  EUNATCH         49  /* Protocol driver not attached */
+#define  ENOCSI          50  /* No CSI structure available */
+#define  EL2HLT          51  /* Level 2 halted */
+#define  EBADE           52  /* Invalid exchange */
+#define  EBADR           53  /* Invalid request descriptor */
+#define  EXFULL          54  /* Exchange full */
+#define  ENOANO          55  /* No anode */
+#define  EBADRQC         56  /* Invalid request code */
+#define  EBADSLT         57  /* Invalid slot */
 
-#define  EDEADLOCK    EDEADLK
+#define  EDEADLOCK       EDEADLK
 
-#define  EBFONT       59  /* Bad font file format */
-#define  ENOSTR       60  /* Device not a stream */
-#define  ENODATA      61  /* No data available */
-#define  ETIME        62  /* Timer expired */
-#define  ENOSR        63  /* Out of streams resources */
-#define  ENONET       64  /* Machine is not on the network */
-#define  ENOPKG       65  /* Package not installed */
-#define  EREMOTE      66  /* Object is remote */
-#define  ENOLINK      67  /* Link has been severed */
-#define  EADV         68  /* Advertise error */
-#define  ESRMNT       69  /* Srmount error */
-#define  ECOMM        70  /* Communication error on send */
-#define  EPROTO       71  /* Protocol error */
-#define  EMULTIHOP    72  /* Multihop attempted */
-#define  EDOTDOT      73  /* RFS specific error */
-#define  EBADMSG      74  /* Not a data message */
-#define  EOVERFLOW    75  /* Value too large for defined data type */
-#define  ENOTUNIQ     76  /* Name not unique on network */
-#define  EBADFD       77  /* File descriptor in bad state */
-#define  EREMCHG      78  /* Remote address changed */
-#define  ELIBACC      79  /* Can not access a needed shared library */
-#define  ELIBBAD      80  /* Accessing a corrupted shared library */
-#define  ELIBSCN      81  /* .lib section in a.out corrupted */
-#define  ELIBMAX      82  /* Attempting to link in too many shared libraries */
-#define  ELIBEXEC     83  /* Cannot exec a shared library directly */
-#define  EILSEQ       84  /* Illegal byte sequence */
-#define  ERESTART     85  /* Interrupted system call should be restarted */
-#define  ESTRPIPE     86  /* Streams pipe error */
-#define  EUSERS       87  /* Too many users */
-#define  ENOTSOCK     88  /* Socket operation on non-socket */
-#define  EDESTADDRREQ 89  /* Destination address required */
-#define  EMSGSIZE     90  /* Message too long */
-#define  EPROTOTYPE   91  /* Protocol wrong type for socket */
-#define  ENOPROTOOPT  92  /* Protocol not available */
+#define  EBFONT          59  /* Bad font file format */
+#define  ENOSTR          60  /* Device not a stream */
+#define  ENODATA         61  /* No data available */
+#define  ETIME           62  /* Timer expired */
+#define  ENOSR           63  /* Out of streams resources */
+#define  ENONET          64  /* Machine is not on the network */
+#define  ENOPKG          65  /* Package not installed */
+#define  EREMOTE         66  /* Object is remote */
+#define  ENOLINK         67  /* Link has been severed */
+#define  EADV            68  /* Advertise error */
+#define  ESRMNT          69  /* Srmount error */
+#define  ECOMM           70  /* Communication error on send */
+#define  EPROTO          71  /* Protocol error */
+#define  EMULTIHOP       72  /* Multihop attempted */
+#define  EDOTDOT         73  /* RFS specific error */
+#define  EBADMSG         74  /* Not a data message */
+#define  EOVERFLOW       75  /* Value too large for defined data type */
+#define  ENOTUNIQ        76  /* Name not unique on network */
+#define  EBADFD          77  /* File descriptor in bad state */
+#define  EREMCHG         78  /* Remote address changed */
+#define  ELIBACC         79  /* Can not access a needed shared library */
+#define  ELIBBAD         80  /* Accessing a corrupted shared library */
+#define  ELIBSCN         81  /* .lib section in a.out corrupted */
+#define  ELIBMAX         82  /* Attempting to link in too many shared libraries */
+#define  ELIBEXEC        83  /* Cannot exec a shared library directly */
+#define  EILSEQ          84  /* Illegal byte sequence */
+#define  ERESTART        85  /* Interrupted system call should be restarted */
+#define  ESTRPIPE        86  /* Streams pipe error */
+#define  EUSERS          87  /* Too many users */
+#define  ENOTSOCK        88  /* Socket operation on non-socket */
+#define  EDESTADDRREQ    89  /* Destination address required */
+#define  EMSGSIZE        90  /* Message too long */
+#define  EPROTOTYPE      91  /* Protocol wrong type for socket */
+#define  ENOPROTOOPT     92  /* Protocol not available */
 #define  EPROTONOSUPPORT 93  /* Protocol not supported */
 #define  ESOCKTNOSUPPORT 94  /* Socket type not supported */
 #define  EOPNOTSUPP      95  /* Operation not supported on transport endpoint */