gsub cannot handle replacing a single backslash using expected syntax

[TylerHilsabeckCVC]

mutate{ gsub => ["message", "//", ""] }
This will fail upon config check with the following error.
The given configuration is invalid. Reason: Expected one of #, {, ,, ] at line 10, column 32 (byte 159) after filter{ mutate{ gsub => ["message", "\\", "
Workaround is
mutate{ gsub => ["message", "[//]{1}", ""] }