diff --git a/include/cxx/cunistd b/include/cxx/cunistd
index 5ea58cf090..86238262ec 100644
--- a/include/cxx/cunistd
+++ b/include/cxx/cunistd
@@ -71,7 +71,9 @@ namespace std
 
   // Terminal I/O
 
+#ifdef CONFIG_SERIAL_TERMIOS
   using ::isatty;
+#endif
 
   // Memory management
 
diff --git a/include/stdio.h b/include/stdio.h
index 1ee68a7518..39180644b3 100644
--- a/include/stdio.h
+++ b/include/stdio.h
@@ -163,8 +163,12 @@ ssize_t getline(FAR char **lineptr, size_t *n, FAR FILE *stream);
 FAR char *gets(FAR char *s);
 FAR char *gets_s(FAR char *s, rsize_t n);
 void   rewind(FAR FILE *stream);
+
+#ifndef CONFIG_STDIO_DISABLE_BUFFERING
 void   setbuf(FAR FILE *stream, FAR char *buf);
 int    setvbuf(FAR FILE *stream, FAR char *buffer, int mode, size_t size);
+#endif
+
 int    ungetc(int c, FAR FILE *stream);
 
 /* Operations on the stdout stream, buffers, paths,
diff --git a/include/termios.h b/include/termios.h
index 291b3f3070..218e4afd29 100644
--- a/include/termios.h
+++ b/include/termios.h
@@ -44,6 +44,8 @@
 #include <sys/types.h>
 #include <stdint.h>
 
+#ifdef CONFIG_SERIAL_TERMIOS
+
 /****************************************************************************
  * Pre-processor Definitions
  ****************************************************************************/
@@ -325,4 +327,5 @@ int tcsetattr(int fd, int options, FAR const struct termios *termiosp);
 }
 #endif
 
+#endif /* CONFIG_SERIAL_TERMIOS */
 #endif /* __INCLUDE_TERMIOS_H */
diff --git a/include/unistd.h b/include/unistd.h
index 4a86e5631c..99dbed4fea 100644
--- a/include/unistd.h
+++ b/include/unistd.h
@@ -327,9 +327,11 @@ ssize_t pread(int fd, FAR void *buf, size_t nbytes, off_t offset);
 ssize_t pwrite(int fd, FAR const void *buf, size_t nbytes, off_t offset);
 int     ftruncate(int fd, off_t length);
 
+#ifdef CONFIG_SERIAL_TERMIOS
 /* Check if a file descriptor corresponds to a terminal I/O file */
 
 int     isatty(int fd);
+#endif
 
 /* Memory management */