diff --git a/doc/jemalloc.xml.in b/doc/jemalloc.xml.in
index d8e2e71..330ba2a 100644
--- a/doc/jemalloc.xml.in
+++ b/doc/jemalloc.xml.in
@@ -57,12 +57,23 @@
     <para>This manual describes jemalloc @jemalloc_version@.  More information
     can be found at the <ulink
     url="http://www.canonware.com/jemalloc/">jemalloc website</ulink>.</para>
+
+    <para>The following configuration options are enabled in libc's built-in
+    jemalloc: <option>--enable-dss</option>,
+    <option>--enable-experimental</option>, <option>--enable-fill</option>,
+    <option>--enable-lazy-lock</option>, <option>--enable-munmap</option>,
+    <option>--enable-stats</option>, <option>--enable-tcache</option>,
+    <option>--enable-tls</option>, <option>--enable-utrace</option>, and
+    <option>--enable-xmalloc</option>.  Additionally,
+    <option>--enable-debug</option> is enabled in development versions of
+    FreeBSD (controlled by the <constant>MALLOC_PRODUCTION</constant> make
+    variable).</para>
   </refsect1>
   <refsynopsisdiv>
     <title>SYNOPSIS</title>
     <funcsynopsis>
       <funcsynopsisinfo>#include &lt;<filename class="headerfile">stdlib.h</filename>&gt;
-#include &lt;<filename class="headerfile">jemalloc/jemalloc.h</filename>&gt;</funcsynopsisinfo>
+#include &lt;<filename class="headerfile">malloc_np.h</filename>&gt;</funcsynopsisinfo>
       <refsect2>
         <title>Standard API</title>
         <funcprototype>
@@ -2342,4 +2353,19 @@ malloc_conf = "lg_chunk:24";]]></programlisting></para>
     <para>The <function>posix_memalign<parameter/></function> function conforms
     to IEEE Std 1003.1-2001 (&ldquo;POSIX.1&rdquo;).</para>
   </refsect1>
+  <refsect1 id="history">
+    <title>HISTORY</title>
+    <para>The <function>malloc_usable_size<parameter/></function> and
+    <function>posix_memalign<parameter/></function> functions first appeared in
+    FreeBSD 7.0.</para>
+
+    <para>The <function>aligned_alloc<parameter/></function>,
+    <function>malloc_stats_print<parameter/></function>,
+    <function>mallctl*<parameter/></function>, and
+    <function>*allocm<parameter/></function> functions first appeared in
+    FreeBSD 10.0.</para>
+
+    <para>The <function>*allocx<parameter/></function> functions first appeared
+    in FreeBSD 11.0.</para>
+  </refsect1>
 </refentry>
diff --git a/include/jemalloc/internal/jemalloc_internal.h.in b/include/jemalloc/internal/jemalloc_internal.h.in
index 574bbb1..e3eafdf 100644
--- a/include/jemalloc/internal/jemalloc_internal.h.in
+++ b/include/jemalloc/internal/jemalloc_internal.h.in
@@ -1,5 +1,8 @@
 #ifndef JEMALLOC_INTERNAL_H
 #define	JEMALLOC_INTERNAL_H
+#include "libc_private.h"
+#include "namespace.h"
+
 #include <math.h>
 #ifdef _WIN32
 #  include <windows.h>
@@ -65,6 +68,9 @@ typedef intptr_t ssize_t;
 #include <valgrind/memcheck.h>
 #endif
 
+#include "un-namespace.h"
+#include "libc_private.h"
+
 #define	JEMALLOC_NO_DEMANGLE
 #ifdef JEMALLOC_JET
 #  define JEMALLOC_N(n) jet_##n
@@ -99,13 +105,7 @@ static const bool config_fill =
     false
 #endif
     ;
-static const bool config_lazy_lock =
-#ifdef JEMALLOC_LAZY_LOCK
-    true
-#else
-    false
-#endif
-    ;
+static const bool config_lazy_lock = true;
 static const bool config_prof =
 #ifdef JEMALLOC_PROF
     true
diff --git a/include/jemalloc/internal/mutex.h b/include/jemalloc/internal/mutex.h
index de44e14..564d604 100644
--- a/include/jemalloc/internal/mutex.h
+++ b/include/jemalloc/internal/mutex.h
@@ -43,9 +43,6 @@ struct malloc_mutex_s {
 
 #ifdef JEMALLOC_LAZY_LOCK
 extern bool isthreaded;
-#else
-#  undef isthreaded /* Undo private_namespace.h definition. */
-#  define isthreaded true
 #endif
 
 bool	malloc_mutex_init(malloc_mutex_t *mutex);
diff --git a/include/jemalloc/internal/private_symbols.txt b/include/jemalloc/internal/private_symbols.txt
index 93516d2..22f9af9 100644
--- a/include/jemalloc/internal/private_symbols.txt
+++ b/include/jemalloc/internal/private_symbols.txt
@@ -226,7 +226,6 @@ iralloc
 iralloct
 iralloct_realign
 isalloc
-isthreaded
 ivsalloc
 ixalloc
 jemalloc_postfork_child
diff --git a/include/jemalloc/jemalloc_FreeBSD.h b/include/jemalloc/jemalloc_FreeBSD.h
new file mode 100644
index 0000000..94554bc
--- /dev/null
+++ b/include/jemalloc/jemalloc_FreeBSD.h
@@ -0,0 +1,134 @@
+/*
+ * Override settings that were generated in jemalloc_defs.h as necessary.
+ */
+
+#undef JEMALLOC_OVERRIDE_VALLOC
+
+#ifndef MALLOC_PRODUCTION
+#define	JEMALLOC_DEBUG
+#endif
+
+/*
+ * The following are architecture-dependent, so conditionally define them for
+ * each supported architecture.
+ */
+#undef CPU_SPINWAIT
+#undef JEMALLOC_TLS_MODEL
+#undef STATIC_PAGE_SHIFT
+#undef LG_SIZEOF_PTR
+#undef LG_SIZEOF_INT
+#undef LG_SIZEOF_LONG
+#undef LG_SIZEOF_INTMAX_T
+
+#ifdef __i386__
+#  define LG_SIZEOF_PTR		2
+#  define CPU_SPINWAIT		__asm__ volatile("pause")
+#  define JEMALLOC_TLS_MODEL	__attribute__((tls_model("initial-exec")))
+#endif
+#ifdef __ia64__
+#  define LG_SIZEOF_PTR		3
+#endif
+#ifdef __sparc64__
+#  define LG_SIZEOF_PTR		3
+#  define JEMALLOC_TLS_MODEL	__attribute__((tls_model("initial-exec")))
+#endif
+#ifdef __amd64__
+#  define LG_SIZEOF_PTR		3
+#  define CPU_SPINWAIT		__asm__ volatile("pause")
+#  define JEMALLOC_TLS_MODEL	__attribute__((tls_model("initial-exec")))
+#endif
+#ifdef __arm__
+#  define LG_SIZEOF_PTR		2
+#endif
+#ifdef __mips__
+#ifdef __mips_n64
+#  define LG_SIZEOF_PTR		3
+#else
+#  define LG_SIZEOF_PTR		2
+#endif
+#endif
+#ifdef __powerpc64__
+#  define LG_SIZEOF_PTR		3
+#elif defined(__powerpc__)
+#  define LG_SIZEOF_PTR		2
+#endif
+
+#ifndef JEMALLOC_TLS_MODEL
+#  define JEMALLOC_TLS_MODEL	/* Default. */
+#endif
+
+#define	STATIC_PAGE_SHIFT	PAGE_SHIFT
+#define	LG_SIZEOF_INT		2
+#define	LG_SIZEOF_LONG		LG_SIZEOF_PTR
+#define	LG_SIZEOF_INTMAX_T	3
+
+/* Disable lazy-lock machinery, mangle isthreaded, and adjust its type. */
+#undef JEMALLOC_LAZY_LOCK
+extern int __isthreaded;
+#define	isthreaded		((bool)__isthreaded)
+
+/* Mangle. */
+#undef je_malloc
+#undef je_calloc
+#undef je_realloc
+#undef je_free
+#undef je_posix_memalign
+#undef je_malloc_usable_size
+#undef je_mallocx
+#undef je_rallocx
+#undef je_xallocx
+#undef je_sallocx
+#undef je_dallocx
+#undef je_nallocx
+#undef je_allocm
+#undef je_rallocm
+#undef je_sallocm
+#undef je_dallocm
+#undef je_nallocm
+#define	je_malloc		__malloc
+#define	je_calloc		__calloc
+#define	je_realloc		__realloc
+#define	je_free			__free
+#define	je_posix_memalign	__posix_memalign
+#define	je_malloc_usable_size	__malloc_usable_size
+#define	je_mallocx		__mallocx
+#define	je_rallocx		__rallocx
+#define	je_xallocx		__xallocx
+#define	je_sallocx		__sallocx
+#define	je_dallocx		__dallocx
+#define	je_nallocx		__nallocx
+#define	je_allocm		__allocm
+#define	je_rallocm		__rallocm
+#define	je_sallocm		__sallocm
+#define	je_dallocm		__dallocm
+#define	je_nallocm		__nallocm
+#define	open			_open
+#define	read			_read
+#define	write			_write
+#define	close			_close
+#define	pthread_mutex_lock	_pthread_mutex_lock
+#define	pthread_mutex_unlock	_pthread_mutex_unlock
+
+#ifdef JEMALLOC_C_
+/*
+ * Define 'weak' symbols so that an application can have its own versions
+ * of malloc, calloc, realloc, free, et al.
+ */
+__weak_reference(__malloc, malloc);
+__weak_reference(__calloc, calloc);
+__weak_reference(__realloc, realloc);
+__weak_reference(__free, free);
+__weak_reference(__posix_memalign, posix_memalign);
+__weak_reference(__malloc_usable_size, malloc_usable_size);
+__weak_reference(__mallocx, mallocx);
+__weak_reference(__rallocx, rallocx);
+__weak_reference(__xallocx, xallocx);
+__weak_reference(__sallocx, sallocx);
+__weak_reference(__dallocx, dallocx);
+__weak_reference(__nallocx, nallocx);
+__weak_reference(__allocm, allocm);
+__weak_reference(__rallocm, rallocm);
+__weak_reference(__sallocm, sallocm);
+__weak_reference(__dallocm, dallocm);
+__weak_reference(__nallocm, nallocm);
+#endif
diff --git a/include/jemalloc/jemalloc_rename.sh b/include/jemalloc/jemalloc_rename.sh
index f943891..47d032c 100755
--- a/include/jemalloc/jemalloc_rename.sh
+++ b/include/jemalloc/jemalloc_rename.sh
@@ -19,4 +19,6 @@ done
 
 cat <<EOF
 #endif
+
+#include "jemalloc_FreeBSD.h"
 EOF
diff --git a/src/jemalloc.c b/src/jemalloc.c
index 204778b..9e5f2df 100644
--- a/src/jemalloc.c
+++ b/src/jemalloc.c
@@ -8,6 +8,10 @@ malloc_tsd_data(, arenas, arena_t *, NULL)
 malloc_tsd_data(, thread_allocated, thread_allocated_t,
     THREAD_ALLOCATED_INITIALIZER)
 
+/* Work around <http://llvm.org/bugs/show_bug.cgi?id=12623>: */
+const char	*__malloc_options_1_0 = NULL;
+__sym_compat(_malloc_options, __malloc_options_1_0, FBSD_1.0);
+
 /* Runtime configuration options. */
 const char	*je_malloc_conf;
 bool	opt_abort =
@@ -457,7 +461,8 @@ malloc_conf_init(void)
 #endif
 			    ;
 
-			if ((opts = getenv(envname)) != NULL) {
+			if (issetugid() == 0 && (opts = getenv(envname)) !=
+			    NULL) {
 				/*
 				 * Do nothing; opts is already initialized to
 				 * the value of the MALLOC_CONF environment
diff --git a/src/mutex.c b/src/mutex.c
index 788eca3..6f5954e 100644
--- a/src/mutex.c
+++ b/src/mutex.c
@@ -66,6 +66,17 @@ pthread_create(pthread_t *__restrict thread,
 #ifdef JEMALLOC_MUTEX_INIT_CB
 JEMALLOC_EXPORT int	_pthread_mutex_init_calloc_cb(pthread_mutex_t *mutex,
     void *(calloc_cb)(size_t, size_t));
+
+__weak_reference(_pthread_mutex_init_calloc_cb_stub,
+    _pthread_mutex_init_calloc_cb);
+
+int
+_pthread_mutex_init_calloc_cb_stub(pthread_mutex_t *mutex,
+    void *(calloc_cb)(size_t, size_t))
+{
+
+	return (0);
+}
 #endif
 
 bool
diff --git a/src/util.c b/src/util.c
index 93a19fd..70b3e45 100644
--- a/src/util.c
+++ b/src/util.c
@@ -58,6 +58,22 @@ wrtmessage(void *cbopaque, const char *s)
 
 JEMALLOC_EXPORT void	(*je_malloc_message)(void *, const char *s);
 
+JEMALLOC_ATTR(visibility("hidden"))
+void
+wrtmessage_1_0(const char *s1, const char *s2, const char *s3,
+    const char *s4)
+{
+
+	wrtmessage(NULL, s1);
+	wrtmessage(NULL, s2);
+	wrtmessage(NULL, s3);
+	wrtmessage(NULL, s4);
+}
+
+void	(*__malloc_message_1_0)(const char *s1, const char *s2, const char *s3,
+    const char *s4) = wrtmessage_1_0;
+__sym_compat(_malloc_message, __malloc_message_1_0, FBSD_1.0);
+
 /*
  * Wrapper around malloc_message() that avoids the need for
  * je_malloc_message(...) throughout the code.