diff --git a/libc/Android.mk b/libc/Android.mk
index 374ffa6..ac7cd75 100644
--- a/libc/Android.mk
+++ b/libc/Android.mk
@@ -133,6 +133,7 @@
     bionic/lockf.cpp \
     bionic/lstat.cpp \
     bionic/malloc_info.cpp \
+    bionic/mblen.cpp \
     bionic/mbrtoc16.cpp \
     bionic/mbrtoc32.cpp \
     bionic/mbstate.cpp \
diff --git a/libc/bionic/mblen.cpp b/libc/bionic/mblen.cpp
new file mode 100644
index 0000000..7def6f1
--- /dev/null
+++ b/libc/bionic/mblen.cpp
@@ -0,0 +1,35 @@
+/*
+ * Copyright (C) 2016 The Android Open Source Project
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *  * Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *  * Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <stdlib.h>
+#include <wchar.h>
+
+int mblen(const char* s, size_t n) {
+  mbstate_t state = {};
+  return mbrlen(s, n, &state);
+}
diff --git a/libc/include/stdlib.h b/libc/include/stdlib.h
index 2abaec3..ba4b149 100644
--- a/libc/include/stdlib.h
+++ b/libc/include/stdlib.h
@@ -162,14 +162,11 @@
 extern const char* getprogname(void);
 extern void setprogname(const char*);
 
-/* make STLPort happy */
-extern int      mblen(const char *, size_t) __UNAVAILABLE;
-extern size_t   mbstowcs(wchar_t *, const char *, size_t);
-extern int      mbtowc(wchar_t *, const char *, size_t);
-
-/* Likewise, make libstdc++-v3 happy.  */
-extern int	wctomb(char *, wchar_t);
-extern size_t	wcstombs(char *, const wchar_t *, size_t);
+int mblen(const char*, size_t);
+size_t mbstowcs(wchar_t*, const char*, size_t);
+int mbtowc(wchar_t*, const char*, size_t);
+int wctomb(char*, wchar_t);
+size_t wcstombs(char*, const wchar_t*, size_t);
 
 extern size_t __ctype_get_mb_cur_max(void);
 #define MB_CUR_MAX __ctype_get_mb_cur_max()
diff --git a/libc/libc.arm.brillo.map b/libc/libc.arm.brillo.map
index 3e78e30..a1373d8 100644
--- a/libc/libc.arm.brillo.map
+++ b/libc/libc.arm.brillo.map
@@ -1279,6 +1279,7 @@
     getpwent;
     getsubopt;
     hasmntopt;
+    mblen;
     pthread_getname_np;
     quotactl;
     setdomainname;
diff --git a/libc/libc.arm.map b/libc/libc.arm.map
index 420cd7e..4e69bf1 100644
--- a/libc/libc.arm.map
+++ b/libc/libc.arm.map
@@ -1279,6 +1279,7 @@
     getpwent;
     getsubopt;
     hasmntopt;
+    mblen;
     pthread_getname_np;
     quotactl;
     setdomainname;
diff --git a/libc/libc.arm64.map b/libc/libc.arm64.map
index bdde35e..7ea74a6 100644
--- a/libc/libc.arm64.map
+++ b/libc/libc.arm64.map
@@ -1201,6 +1201,7 @@
     getpwent;
     getsubopt;
     hasmntopt;
+    mblen;
     pthread_getname_np;
     quotactl;
     setdomainname;
diff --git a/libc/libc.map.txt b/libc/libc.map.txt
index be37ffb..8d1a1f9 100644
--- a/libc/libc.map.txt
+++ b/libc/libc.map.txt
@@ -1304,6 +1304,7 @@
     getpwent;
     getsubopt;
     hasmntopt;
+    mblen;
     pthread_getname_np;
     quotactl;
     setdomainname;
diff --git a/libc/libc.mips.brillo.map b/libc/libc.mips.brillo.map
index 6b5744c..aac1d8c 100644
--- a/libc/libc.mips.brillo.map
+++ b/libc/libc.mips.brillo.map
@@ -1263,6 +1263,7 @@
     getpwent;
     getsubopt;
     hasmntopt;
+    mblen;
     pthread_getname_np;
     quotactl;
     setdomainname;
diff --git a/libc/libc.mips.map b/libc/libc.mips.map
index 6ee9cf5..e514aa1 100644
--- a/libc/libc.mips.map
+++ b/libc/libc.mips.map
@@ -1263,6 +1263,7 @@
     getpwent;
     getsubopt;
     hasmntopt;
+    mblen;
     pthread_getname_np;
     quotactl;
     setdomainname;
diff --git a/libc/libc.mips64.map b/libc/libc.mips64.map
index bdde35e..7ea74a6 100644
--- a/libc/libc.mips64.map
+++ b/libc/libc.mips64.map
@@ -1201,6 +1201,7 @@
     getpwent;
     getsubopt;
     hasmntopt;
+    mblen;
     pthread_getname_np;
     quotactl;
     setdomainname;
diff --git a/libc/libc.x86.brillo.map b/libc/libc.x86.brillo.map
index d483d3e..f14861d 100644
--- a/libc/libc.x86.brillo.map
+++ b/libc/libc.x86.brillo.map
@@ -1261,6 +1261,7 @@
     getpwent;
     getsubopt;
     hasmntopt;
+    mblen;
     pthread_getname_np;
     quotactl;
     setdomainname;
diff --git a/libc/libc.x86.map b/libc/libc.x86.map
index f0679c0..f6b6ea1 100644
--- a/libc/libc.x86.map
+++ b/libc/libc.x86.map
@@ -1261,6 +1261,7 @@
     getpwent;
     getsubopt;
     hasmntopt;
+    mblen;
     pthread_getname_np;
     quotactl;
     setdomainname;
diff --git a/libc/libc.x86_64.map b/libc/libc.x86_64.map
index bdde35e..7ea74a6 100644
--- a/libc/libc.x86_64.map
+++ b/libc/libc.x86_64.map
@@ -1201,6 +1201,7 @@
     getpwent;
     getsubopt;
     hasmntopt;
+    mblen;
     pthread_getname_np;
     quotactl;
     setdomainname;