diff --git a/lib/libthr/Makefile b/lib/libthr/Makefile
index 1a5dfa18dca7..038823413cb2 100644
--- a/lib/libthr/Makefile
+++ b/lib/libthr/Makefile
@@ -1,73 +1,79 @@
 # $FreeBSD$
 #
 # All library objects contain FreeBSD revision strings by default; they may be
 # excluded as a space-saving measure.  To produce a library that does
 # not contain these strings, add -DSTRIP_FBSDID (see <sys/cdefs.h>) to CFLAGS
 # below.
 
 PACKAGE=	clibs
 SHLIBDIR?= /lib
 
 .include <src.opts.mk>
 MK_SSP=	no
 
 LIB=thr
 SHLIB_MAJOR= 3
 NO_WTHREAD_SAFETY=1
 NO_WCAST_ALIGN.gcc=1    # for gcc 4.2
 CFLAGS+=-DPTHREAD_KERNEL
 CFLAGS+=-I${SRCTOP}/lib/libc/include
 CFLAGS+=-I${SRCTOP}/lib/libc/${MACHINE_CPUARCH}
 CFLAGS+=-I${.CURDIR}/thread
 CFLAGS+=-I${SRCTOP}/include
 CFLAGS+=-I${.CURDIR}/arch/${MACHINE_CPUARCH}/include
 CFLAGS+=-I${.CURDIR}/sys
 CFLAGS+=-I${SRCTOP}/libexec/rtld-elf
 CFLAGS+=-I${SRCTOP}/libexec/rtld-elf/${MACHINE_CPUARCH}
 CFLAGS+=-I${SRCTOP}/lib/libthread_db
 
 CFLAGS.thr_stack.c+=	-Wno-cast-align
 CFLAGS.rtld_malloc.c+=	-Wno-cast-align
 CFLAGS.thr_symbols.c+=	-Wno-missing-variable-declarations
+.if ${MK_ASAN} != "no"
+# False-positive ASAN error claiming the local "struct sigaction act;" is
+# overflowed by handle_signal() reading from the ucontext_t argument. This
+# could be caused by ASAN not treating this function as a signal handler.
+CFLAGS.thr_sig.c+=	-fno-sanitize=address
+.endif
 
 .ifndef NO_THREAD_UNWIND_STACK
 CFLAGS+=-fexceptions
 CFLAGS+=-D_PTHREAD_FORCED_UNWIND
 .endif
 
 LDFLAGS+=-Wl,-znodelete
 
 VERSION_DEF=${SRCTOP}/lib/libc/Versions.def
 SYMBOL_MAPS=${.CURDIR}/pthread.map
 
 MAN=	libthr.3
 
 # enable extra internal consistency checks
 CFLAGS+=-D_PTHREADS_INVARIANTS
 
 PRECIOUSLIB=
 
 .PATH: ${.CURDIR}/arch/${MACHINE_CPUARCH}/${MACHINE_CPUARCH}
 .PATH: ${SRCTOP}/libexec/rtld-elf
 
 .if exists(${.CURDIR}/arch/${MACHINE_CPUARCH}/Makefile.inc)
 .include "${.CURDIR}/arch/${MACHINE_CPUARCH}/Makefile.inc"
 .endif
 .include "${.CURDIR}/sys/Makefile.inc"
 .include "${.CURDIR}/thread/Makefile.inc"
 SRCS+= rtld_malloc.c
 
 .if ${MK_INSTALLLIB} != "no"
 SYMLINKS+=lib${LIB}.a ${LIBDIR}/libpthread.a
 .endif
 .if !defined(NO_PIC)
 SYMLINKS+=lib${LIB}.so ${LIBDIR}/libpthread.so
 .endif
 .if ${MK_PROFILE} != "no"
 SYMLINKS+=lib${LIB}_p.a ${LIBDIR}/libpthread_p.a
 .endif
 
 HAS_TESTS=
 SUBDIR.${MK_TESTS}+= tests
 
 .include <bsd.lib.mk>