diff --git a/libr/core/cmd_write.c b/libr/core/cmd_write.c
index c900468b54..45aa4c4808 100644
--- a/libr/core/cmd_write.c
+++ b/libr/core/cmd_write.c
@@ -130,7 +130,9 @@ static void cmd_write_value (RCore *core, const char *input) {
 	case '8': type = 8; break;
 	}
 	off = r_num_math (core->num, input+2);
-	r_io_use_desc (core->io, core->file->desc);
+	if (core->file) {
+		r_io_use_desc (core->io, core->file->desc);
+	}
 	r_io_seek (core->io, core->offset, R_IO_SEEK_SET);
 	if (type == 0)
 		type = (off&UT64_32U)? 8: 4;
@@ -183,6 +185,7 @@ static int cmd_write(void *data, const char *input) {
 		"waf"," file","assemble file and write bytes",
 		"wA"," r 0","alter/modify opcode at current seek (see wA?)",
 		"wb"," 010203","fill current block with cyclic hexpairs",
+		"wB","[-]0xVALUE","set or unset bits with given value",
 		"wc","","list all write changes",
 		"wc","[ir*?]","write cache undo/commit/reset/list (io.cache)",
 		"wd"," [off] [n]","duplicate N bytes from offset at current seek (memcpy) (see y?)",
diff --git a/libr/io/io.c b/libr/io/io.c
index d7e222371b..c573a6894a 100644
--- a/libr/io/io.c
+++ b/libr/io/io.c
@@ -653,16 +653,21 @@ R_API int r_io_write(RIO *io, const ut8 *buf, int len) {
 			ret = -1;
 		}
 	} else {
-		ret = write (io->desc->fd, buf, len);
+		if (io->desc) {
+			ret = write (io->desc->fd, buf, len);
+		} else ret = -1;
 	}
 	if (ret == -1) {
 		if (io->cached != 2) {
-			eprintf ("r_io_write: cannot write on fd %d\n", io->desc->fd);
+			eprintf ("r_io_write: cannot write on fd %d\n",
+				io->desc? io->desc->fd: -1);
 			r_io_cache_invalidate (io, io->off, io->off+1);
 		}
 	} else {
-		r_io_map_write_update (io, io->desc->fd, io->off, ret);
-		io->off += ret;
+		if (io->desc) {
+			r_io_map_write_update (io, io->desc->fd, io->off, ret);
+			io->off += ret;
+		}
 	}
 	free (data);
 	return ret;
diff --git a/sys/duktape.sh b/sys/duktape.sh
index 3d923f96f7..25ae25a57f 100755
--- a/sys/duktape.sh
+++ b/sys/duktape.sh
@@ -5,6 +5,10 @@ cd `dirname $PWD/$0`
 ./clone-r2-bindings.sh
 cd ..
 
+# workaround for osx
+if [ -f /usr/lib/pkgconfig/r_util.pc ]; then
+	export PKG_CONFIG_PATH=/usr/lib/pkgconfig
+fi
 [ -z "${PREFIX}" ] && PREFIX=/usr
 ID=`id -u` 
 [ -n "${NOSUDO}" ] && SUDO=
@@ -12,11 +16,11 @@ ID=`id -u`
 export DESTDIR
 
 cd radare2-bindings
-./configure --prefix=/usr --enable=duktape
+./configure --prefix=/usr --enable=duktape || exit 1
 cd libr/lang/p
 make clean
-make
-rm ~/.config/radare2/plugins/lang_duktape.*
+make || exit 1
+rm -f ~/.config/radare2/plugins/lang_duktape.*
 if [ "$1" != '--no-install' ]; then
 	if [ "$ID" = 0 ]; then
 		${SUDO} make install DESTDIR=${DESTDIR}