diff --git a/CHANGES b/CHANGES
index 0649a5307..655d78fb1 100644
--- a/CHANGES
+++ b/CHANGES
@@ -1,5 +1,8 @@
 CHANGES FROM 3.7b TO 3.7c
 
+* Build with jemalloc on macOS to avoid what appears to be a bug in calloc
+  (issue 5385).
+
 * Fix scrollbar initial state so they appear on new windows (issue 5339).
 
 * Check time periodically in loops rather than every one (issue 5367).
diff --git a/configure.ac b/configure.ac
index d2b61376b..56cef0848 100644
--- a/configure.ac
+++ b/configure.ac
@@ -76,9 +76,7 @@ AM_CONDITIONAL(IS_OPTIMIZED, test "x$enable_optimizations" = xyes)
 # Is this --enable-asan?
 AC_ARG_ENABLE(
 	asan,
-	AS_HELP_STRING(--enable-asan, enable ASAN build flags),
-	,
-	enable_asan=no
+	AS_HELP_STRING(--enable-asan, enable ASAN build flags)
 )
 AM_CONDITIONAL(IS_ASAN, test "x$enable_asan" = xyes)
 
@@ -241,6 +239,7 @@ AC_LIBOBJ(getopt_long)
 
 # Look for libevent. Try libevent_core or libevent with pkg-config first then
 # look for the library.
+libevent_version=off
 PKG_CHECK_MODULES(
 	LIBEVENT_CORE,
 	[libevent_core >= 2],
@@ -249,6 +248,8 @@ PKG_CHECK_MODULES(
 		CPPFLAGS="$AM_CPPFLAGS $SAVED_CPPFLAGS"
 		LIBS="$LIBEVENT_CORE_LIBS $LIBS"
 		found_libevent=yes
+		libevent_version=`$PKG_CONFIG --modversion libevent_core 2>/dev/null`
+		test "x$libevent_version" = x && libevent_version=on
 	],
 	found_libevent=no
 )
@@ -261,6 +262,8 @@ if test x$found_libevent = xno; then
 			CPPFLAGS="$AM_CPPFLAGS $SAVED_CPPFLAGS"
 			LIBS="$LIBEVENT_LIBS $LIBS"
 			found_libevent=yes
+			libevent_version=`$PKG_CONFIG --modversion libevent 2>/dev/null`
+			test "x$libevent_version" = x && libevent_version=on
 		],
 		found_libevent=no
 	)
@@ -269,7 +272,8 @@ if test x$found_libevent = xno; then
 	AC_SEARCH_LIBS(
 		event_init,
 		[event_core event event-1.4],
-		found_libevent=yes,
+		[found_libevent=yes
+		libevent_version=on],
 		found_libevent=no
 	)
 fi
@@ -296,6 +300,7 @@ fi
 
 # Look for ncurses or curses. Try pkg-config first then directly for the
 # library.
+ncurses_version=off
 PKG_CHECK_MODULES(
 	LIBTINFOW,
 	tinfow,
@@ -304,6 +309,8 @@ PKG_CHECK_MODULES(
 		CPPFLAGS="$LIBTINFOW_CFLAGS $SAVED_CPPFLAGS"
 		LIBS="$LIBTINFOW_LIBS $LIBS"
 		found_ncurses=yes
+		ncurses_version=`$PKG_CONFIG --modversion tinfow 2>/dev/null`
+		test "x$ncurses_version" = x && ncurses_version=on
 	],
 	found_ncurses=no
 )
@@ -316,6 +323,8 @@ if test "x$found_ncurses" = xno; then
 			CPPFLAGS="$LIBTINFO_CFLAGS $SAVED_CPPFLAGS"
 			LIBS="$LIBTINFO_LIBS $LIBS"
 			found_ncurses=yes
+			ncurses_version=`$PKG_CONFIG --modversion tinfo 2>/dev/null`
+			test "x$ncurses_version" = x && ncurses_version=on
 		],
 		found_ncurses=no
 	)
@@ -329,6 +338,8 @@ if test "x$found_ncurses" = xno; then
 			CPPFLAGS="$LIBNCURSESW_CFLAGS $SAVED_CPPFLAGS"
 			LIBS="$LIBNCURSESW_LIBS $LIBS"
 			found_ncurses=yes
+			ncurses_version=`$PKG_CONFIG --modversion ncursesw 2>/dev/null`
+			test "x$ncurses_version" = x && ncurses_version=on
 		],
 		found_ncurses=no
 	)
@@ -342,6 +353,8 @@ if test "x$found_ncurses" = xno; then
 			CPPFLAGS="$LIBNCURSES_CFLAGS $SAVED_CPPFLAGS"
 			LIBS="$LIBNCURSES_LIBS $LIBS"
 			found_ncurses=yes
+			ncurses_version=`$PKG_CONFIG --modversion ncurses 2>/dev/null`
+			test "x$ncurses_version" = x && ncurses_version=on
 		],
 		found_ncurses=no
 	)
@@ -350,7 +363,8 @@ if test "x$found_ncurses" = xno; then
 	AC_SEARCH_LIBS(
 		setupterm,
 		[tinfow tinfo terminfo ncursesw ncurses],
-		found_ncurses=yes,
+		[found_ncurses=yes
+		ncurses_version=on],
 		found_ncurses=no
 	)
 	if test "x$found_ncurses" = xyes; then
@@ -380,6 +394,7 @@ else
 		LIBS="$LIBS -lcurses"
 		CPPFLAGS="$CPPFLAGS -DHAVE_CURSES_H"
 		AC_DEFINE(HAVE_CURSES_H)
+		ncurses_version=on
 	else
 		AC_MSG_ERROR("curses not found")
 	fi
@@ -390,6 +405,7 @@ AC_CHECK_FUNCS([ \
 ])
 
 # Look for utempter.
+utempter_version=off
 AC_ARG_ENABLE(
 	utempter,
 	AS_HELP_STRING(--enable-utempter, use utempter if it is installed)
@@ -406,17 +422,34 @@ if test "x$enable_utempter" = xyes; then
 	fi
 	if test "x$enable_utempter" = xyes; then
 		AC_DEFINE(HAVE_UTEMPTER)
+		utempter_version=on
 	else
 		AC_MSG_ERROR("utempter not found")
 	fi
 fi
 
 # Look for utf8proc.
+utf8proc_version=off
 AC_ARG_ENABLE(
 	utf8proc,
 	AS_HELP_STRING(--enable-utf8proc, use utf8proc if it is installed)
 )
+try_utf8proc=no
+require_utf8proc=no
 if test "x$enable_utf8proc" = xyes; then
+	try_utf8proc=yes
+elif test "x$enable_utf8proc" = x; then
+	case "$host_os" in
+		*darwin*)
+			try_utf8proc=yes
+			require_utf8proc=yes
+			;;
+	esac
+fi
+if test "x$try_utf8proc" = xyes; then
+	SAVED_AM_CPPFLAGS="$AM_CPPFLAGS"
+	SAVED_OLD_CPPFLAGS="$CPPFLAGS"
+	SAVED_LIBS="$LIBS"
 	PKG_CHECK_MODULES(
 		LIBUTF8PROC,
 		libutf8proc,
@@ -424,7 +457,10 @@ if test "x$enable_utf8proc" = xyes; then
 			AM_CPPFLAGS="$LIBUTF8PROC_CFLAGS $AM_CPPFLAGS"
 			CPPFLAGS="$LIBUTF8PROC_CFLAGS $SAVED_CPPFLAGS"
 			LIBS="$LIBUTF8PROC_LIBS $LIBS"
-		]
+			utf8proc_version=`$PKG_CONFIG --modversion libutf8proc 2>/dev/null`
+			test "x$utf8proc_version" = x && utf8proc_version=on
+		],
+		[:]
 	)
 	AC_CHECK_HEADER(utf8proc.h, enable_utf8proc=yes, enable_utf8proc=no)
 	if test "x$enable_utf8proc" = xyes; then
@@ -437,13 +473,23 @@ if test "x$enable_utf8proc" = xyes; then
 	fi
 	if test "x$enable_utf8proc" = xyes; then
 		AC_DEFINE(HAVE_UTF8PROC)
+		test "x$utf8proc_version" = xoff && utf8proc_version=on
 	else
-		AC_MSG_ERROR("utf8proc not found")
+		AM_CPPFLAGS="$SAVED_AM_CPPFLAGS"
+		CPPFLAGS="$SAVED_OLD_CPPFLAGS"
+		LIBS="$SAVED_LIBS"
+		utf8proc_version=off
+		if test "x$require_utf8proc" = xyes; then
+			enable_utf8proc=
+		else
+			AC_MSG_ERROR("utf8proc not found")
+		fi
 	fi
 fi
 AM_CONDITIONAL(HAVE_UTF8PROC, [test "x$enable_utf8proc" = xyes])
 
 # Check for systemd support.
+systemd_version=off
 AC_ARG_ENABLE(
 	systemd,
 	AS_HELP_STRING(--enable-systemd, enable systemd integration)
@@ -457,6 +503,8 @@ if test x"$enable_systemd" = xyes; then
 			CPPFLAGS="$AM_CPPFLAGS $SAVED_CPPFLAGS"
 			LIBS="$SYSTEMD_LIBS $LIBS"
 			found_systemd=yes
+			systemd_version=`$PKG_CONFIG --modversion libsystemd 2>/dev/null`
+			test "x$systemd_version" = x && systemd_version=on
 		],
 		found_systemd=no
 	)
@@ -581,11 +629,27 @@ if test "x$found_malloc_trim" = xyes; then
 fi
 
 # Build against jemalloc if requested.
+jemalloc_version=off
 AC_ARG_ENABLE(
 	jemalloc,
 	AS_HELP_STRING(--enable-jemalloc, use jemalloc if it is installed)
 )
+try_jemalloc=no
+require_jemalloc=no
 if test "x$enable_jemalloc" = xyes; then
+	try_jemalloc=yes
+elif test "x$enable_jemalloc" = x; then
+	case "$host_os" in
+		*darwin*)
+			try_jemalloc=yes
+			require_jemalloc=yes
+			;;
+	esac
+fi
+if test "x$try_jemalloc" = xyes; then
+	SAVED_AM_CPPFLAGS="$AM_CPPFLAGS"
+	SAVED_OLD_CPPFLAGS="$CPPFLAGS"
+	SAVED_LIBS="$LIBS"
 	PKG_CHECK_MODULES(
 		JEMALLOC,
 		jemalloc,
@@ -593,9 +657,26 @@ if test "x$enable_jemalloc" = xyes; then
 			AM_CPPFLAGS="$JEMALLOC_CFLAGS $AM_CPPFLAGS"
 			CPPFLAGS="$AM_CPPFLAGS $SAVED_CPPFLAGS"
 			LIBS="$LIBS $JEMALLOC_LIBS"
+			jemalloc_version=`$PKG_CONFIG --modversion jemalloc 2>/dev/null`
+			test "x$jemalloc_version" = x && jemalloc_version=on
 		],
-		AC_MSG_ERROR("jemalloc not found")
+		enable_jemalloc=no
 	)
+	if test "x$enable_jemalloc" = xno; then
+		AM_CPPFLAGS="$SAVED_AM_CPPFLAGS"
+		CPPFLAGS="$SAVED_OLD_CPPFLAGS"
+		LIBS="$SAVED_LIBS"
+		jemalloc_version=off
+		if test "x$require_jemalloc" = xyes; then
+			enable_jemalloc=
+		else
+			AC_MSG_ERROR("jemalloc not found")
+		fi
+	else
+		enable_jemalloc=yes
+		AC_DEFINE(HAVE_JEMALLOC)
+		test "x$jemalloc_version" = xoff && jemalloc_version=on
+	fi
 fi
 
 # Check for CMSG_DATA. On some platforms like HP-UX this requires UNIX 95
@@ -942,6 +1023,20 @@ case "$host_os" in
 			AC_MSG_NOTICE([])
 			AC_MSG_ERROR([must give --enable-utf8proc or --disable-utf8proc])
 		fi
+		#
+		# macOS calloc(3) does not appear to always zero memory correctly,
+		# so complain and suggest using jemalloc instead.
+		#
+		if test "x$enable_jemalloc" = x; then
+			AC_MSG_NOTICE([])
+			AC_MSG_NOTICE([	   macOS calloc(3) appears not to correctly])
+			AC_MSG_NOTICE([	   zero allocations in some circumstances;])
+			AC_MSG_NOTICE([	   to avoid this, configuring with])
+			AC_MSG_NOTICE([	   --enable-jemalloc is recommended. To build])
+			AC_MSG_NOTICE([	   without anyway, use --disable-jemalloc])
+			AC_MSG_NOTICE([])
+			AC_MSG_ERROR([must give --enable-jemalloc or --disable-jemalloc])
+		fi
 		;;
 	*dragonfly*)
 		AC_MSG_RESULT(dragonfly)
@@ -1029,6 +1124,26 @@ AC_MSG_CHECKING(lock-command)
 AC_MSG_RESULT($DEFAULT_LOCK_CMD)
 AC_SUBST(DEFAULT_LOCK_CMD)
 
+# Print a summary.
+AC_MSG_NOTICE([])
+if test "x$enable_asan" = xyes; then
+	AC_MSG_NOTICE([ASAN: on])
+else
+	AC_MSG_NOTICE([ASAN: off])
+fi
+if test "x$enable_debug" = xyes; then
+	AC_MSG_NOTICE([debug: on])
+else
+	AC_MSG_NOTICE([debug: off])
+fi
+AC_MSG_NOTICE([jemalloc: $jemalloc_version])
+AC_MSG_NOTICE([libevent: $libevent_version])
+AC_MSG_NOTICE([ncurses: $ncurses_version])
+AC_MSG_NOTICE([systemd: $systemd_version])
+AC_MSG_NOTICE([utempter: $utempter_version])
+AC_MSG_NOTICE([utf8proc: $utf8proc_version])
+AC_MSG_NOTICE([])
+
 # Save our CFLAGS/CPPFLAGS/LDFLAGS for the Makefile and restore the old user
 # variables.
 AC_SUBST(AM_CPPFLAGS)
diff --git a/proc.c b/proc.c
index 01281d023..16e0a2ccd 100644
--- a/proc.c
+++ b/proc.c
@@ -31,6 +31,10 @@
 #include <ncurses.h>
 #endif
 
+#ifdef HAVE_JEMALLOC
+#include <jemalloc/jemalloc.h>
+#endif
+
 #include "tmux.h"
 
 struct tmuxproc {
@@ -180,6 +184,10 @@ proc_start(const char *name)
 {
 	struct tmuxproc	*tp;
 	struct utsname	 u;
+#ifdef HAVE_JEMALLOC
+	const char	*version;
+	size_t		 size = sizeof version;
+#endif
 
 	log_open(name);
 	setproctitle("%s (%s)", name, socket_path);
@@ -194,6 +202,11 @@ proc_start(const char *name)
 #ifdef HAVE_UTF8PROC
 	log_debug("using utf8proc %s", utf8proc_version());
 #endif
+#ifdef HAVE_JEMALLOC
+	if (mallctl("version", &version, &size, NULL, 0) != 0)
+		version = "(unknown version)";
+	log_debug("using jemalloc %s", version);
+#endif
 #ifdef NCURSES_VERSION
 	log_debug("using ncurses %s %06u", NCURSES_VERSION, NCURSES_VERSION_PATCH);
 #endif