--- a/build/autoconf/jemalloc.m4
+++ b/build/autoconf/jemalloc.m4
@@ -29,16 +29,21 @@ if test "$MOZ_BUILD_APP" != js -o -n "$J
           # See memory/build/mozmemory_wrap.h for details.
           ac_configure_args="$ac_configure_args --without-export"
           ;;
       esac
       if test "${OS_ARCH}" = WINNT; then
         # Lazy lock initialization doesn't play well with lazy linking of
         # mozglue.dll on Windows XP (leads to startup crash), so disable it.
         ac_configure_args="$ac_configure_args --disable-lazy-lock"
+
+        # 64-bit Windows builds require a minimum 16-byte alignment.
+        if test -n "$HAVE_64BIT_BUILD"; then
+          ac_configure_args="$ac_configure_args --with-lg-tiny-min=4"
+        fi
       fi
     elif test "${OS_ARCH}" = Darwin; then
       # When building as a replace-malloc lib, disabling the zone allocator
       # forces to use pthread_atfork.
       ac_configure_args="$ac_configure_args --disable-zone-allocator"
     fi
     _MANGLE="malloc posix_memalign aligned_alloc calloc realloc free memalign valloc malloc_usable_size"
     JEMALLOC_WRAPPER=