Yanking takes an extra character and adds a new line

[offero]

Whenever I yank from vim and paste in tmux I get an extra character and a newline pasted. This is a horrible experience when trying to paste into a terminal because it either creates a newline in the terminal or it enters a command when I am not done modifying it.

By default this should only put into the tmux clipboard the actual contents of what was yanked.

I'm on WSL ubuntu linux.

+ λ nvim --version
NVIM v0.3.1
Build type: Release
LuaJIT 2.1.0-beta3
Compilation: /usr/bin/cc -g -O2 -fdebug-prefix-map=/build/neovim-M0l_b5/neovim-0.3.1=. -fstack-protector-strong -Wformat -Werror=format-security -Wdate-time -D_FORTIFY_SOURCE=2 -DDISABLE_LOG -Wdate-time -D_FORTIFY_SOURCE=2 -Wconversion -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=1 -O2 -DNDEBUG -DMIN_LOG_LEVEL=3 -Wall -Wextra -pedantic -Wno-unused-parameter -Wstrict-prototypes -std=gnu99 -Wimplicit-fallthrough -Wvla -fstack-protector-strong -fdiagnostics-color=auto -Wno-array-bounds -DINCLUDE_GENERATED_DECLARATIONS -D_GNU_SOURCE -DNVIM_MSGPACK_HAS_FLOAT32 -DNVIM_UNIBI_HAS_VAR_FROM -I/build/neovim-M0l_b5/neovim-0.3.1/build/config -I/build/neovim-M0l_b5/neovim-0.3.1/src -I/usr/include -I/build/neovim-M0l_b5/neovim-0.3.1/build/src/nvim/auto -I/build/neovim-M0l_b5/neovim-0.3.1/build/include
Compiled by team+vim@tracker.debian.org

Features: +acl +iconv +jemalloc +tui

+ λ aptitude show tmux
Package: tmux
Version: 2.6-3ubuntu0.1