diff --git a/arch/arm/src/kinetis/chip/kinetis_i2c.h b/arch/arm/src/kinetis/chip/kinetis_i2c.h
index c964cf5e731..95cd965ca84 100644
--- a/arch/arm/src/kinetis/chip/kinetis_i2c.h
+++ b/arch/arm/src/kinetis/chip/kinetis_i2c.h
@@ -251,10 +251,10 @@
 #  define I2C_FLT_SHIFT          (0)       /* Bits 0-3: I2C programmable filter factor */
 #  define I2C_FLT_MASK           (15 << I2C_FLT_SHIFT)
 #    define I2C_FLT(n)           ((uint8_t)(n) << I2C_FLT_SHIFT)
-#  define I2C_FLT_STARTF         (1 << 4) /* I2C bus start detect flag */
-#  define I2C_FLT_SSIE           (1 << 5) /* I2C bus stop or start interrupt enable */
-#  define I2C_FLT_STOPF          (1 << 6) /* I2C bus stop detect flag */
-#  define I2C_FLT_SHEN           (1 << 7) /* Stop hold enable */
+#  define I2C_FLT_STARTF         (1 << 4)  /* I2C bus start detect flag */
+#  define I2C_FLT_SSIE           (1 << 5)  /* I2C bus stop or start interrupt enable */
+#  define I2C_FLT_STOPF          (1 << 6)  /* I2C bus stop detect flag */
+#  define I2C_FLT_SHEN           (1 << 7)  /* Stop hold enable */
 #endif
 
 /* I2C Range Address register (8-bit) */
diff --git a/include/cxx/cunistd b/include/cxx/cunistd
index b2552d778f8..fc437cc9875 100644
--- a/include/cxx/cunistd
+++ b/include/cxx/cunistd
@@ -106,7 +106,11 @@ namespace std
   using ::execv;
 #endif
 
-  // Other
+  // Byte operations
+
+  using ::swab;
+
+  // getopt and friends
 
   using ::getopt;
 
diff --git a/include/unistd.h b/include/unistd.h
index 4453c2d4f46..a812533aada 100644
--- a/include/unistd.h
+++ b/include/unistd.h
@@ -203,7 +203,11 @@ int     execl(FAR const char *path, ...);
 int     execv(FAR const char *path, FAR char *const argv[]);
 #endif
 
-/* Other */
+/* Byte operations */
+
+void    swab(FAR const void *src, FAR void *dest, ssize_t nbytes);
+
+/* getopt and friends */
 
 int     getopt(int argc, FAR char *const argv[], FAR const char *optstring);
 
diff --git a/libc/unistd/Make.defs b/libc/unistd/Make.defs
index 2aa942dd3ff..3234a9f7fc5 100644
--- a/libc/unistd/Make.defs
+++ b/libc/unistd/Make.defs
@@ -1,7 +1,7 @@
 ############################################################################
 # libc/unistd/Make.defs
 #
-#   Copyright (C) 2011-2012 Gregory Nutt. All rights reserved.
+#   Copyright (C) 2011-2012, 2017 Gregory Nutt. All rights reserved.
 #   Author: Gregory Nutt <gnutt@nuttx.org>
 #
 # Redistribution and use in source and binary forms, with or without
@@ -35,8 +35,8 @@
 
 # Add the unistd C files to the build
 
-CSRCS += lib_access.c lib_getopt.c lib_getoptargp.c lib_getoptindp.c
-CSRCS += lib_getoptoptp.c
+CSRCS += lib_access.c lib_swab.c
+CSRCS += lib_getopt.c lib_getoptargp.c lib_getoptindp.c lib_getoptoptp.c
 
 ifneq ($(CONFIG_NFILE_DESCRIPTORS),0)
 ifneq ($(CONFIG_DISABLE_ENVIRON),y)