diff --git a/src/encode.moon b/src/encode.moon
index 1768437..3dc8934 100644
--- a/src/encode.moon
+++ b/src/encode.moon
@@ -143,6 +143,7 @@ get_sub_options = ->
 	append_property(ret, "sub-auto")
 	append_property(ret, "sub-pos")
 	append_property(ret, "sub-delay")
+	append_property(ret, "sub-speed")
 	append_property(ret, "sub-scale")
 	append_property(ret, "sub-font")
 	append_property(ret, "sub-font-size")