diff --git a/lib/libthr/Makefile b/lib/libthr/Makefile
--- a/lib/libthr/Makefile
+++ b/lib/libthr/Makefile
@@ -32,6 +32,7 @@
 
 CFLAGS.thr_stack.c+=	-Wno-cast-align
 CFLAGS.rtld_malloc.c+=	-Wno-cast-align
+CFLAGS.thr_rtld.c+=	-fno-builtin-memcpy
 CFLAGS.thr_symbols.c+=	-Wno-missing-variable-declarations
 .if ${MK_ASAN} != "no"
 # False-positive ASAN error claiming the local "struct sigaction act;" is