diff --git a/libc/Makefile b/libc/Makefile
index f1094961..870591cb 100644
--- a/libc/Makefile
+++ b/libc/Makefile
@@ -538,6 +538,7 @@ stdlib/mkstemps.o \
 stdlib/on_exit.o \
 stdlib/posix_openpt.o \
 stdlib/ptsname.o \
+stdlib/ptsname_r.o \
 stdlib/rand.o \
 stdlib/realpath.o \
 stdlib/setenv.o \
diff --git a/libc/include/stdlib.h b/libc/include/stdlib.h
index f7abebfb..86e1503e 100644
--- a/libc/include/stdlib.h
+++ b/libc/include/stdlib.h
@@ -183,6 +183,7 @@ uint32_t arc4random(void);
 void arc4random_buf(void*, size_t);
 uint32_t arc4random_uniform(uint32_t);
 void* reallocarray(void*, size_t, size_t);
+int ptsname_r(int, char*, size_t);
 #endif
 
 #ifdef __cplusplus
diff --git a/libc/stdlib/ptsname_r.c b/libc/stdlib/ptsname_r.c
new file mode 100644
index 00000000..3f8805c6
--- /dev/null
+++ b/libc/stdlib/ptsname_r.c
@@ -0,0 +1,29 @@
+/*
+ * Copyright (c) 2016 Jonas 'Sortie' Termansen.
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ *
+ * unistd/ptsname_r.c
+ * Returns the path of a pseudoterminal master's slave.
+ */
+
+#include <errno.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+int ptsname_r(int fd, char* path, size_t path_size)
+{
+	if ( ttyname_r(fd, path, path_size) < 0 )
+		return errno;
+	return 0;
+}