Comment 14 for bug 885070

I'll add that berend's suggestion (#11) fits my case. To solve, I inspected settings using gsettings and I found number-of-desktops set to "2". When I set it to 1 (which I believe is the default value) the problem went away.

Here's an example from console:

# Find the keys I'm looking for.
gsettings list-keys org.compiz.core:/org/compiz/profiles/unity/plugins/core/
...
hsize
vsize
number-of-desktops
...

# Get the current value for number-of-desktops
gsettings get org.compiz.core:/org/compiz/profiles/unity/plugins/core/ number-of-desktops
2

# Set my desired values for number-of-desktops, and number of workspaces.
gsettings set org.compiz.core:/org/compiz/profiles/unity/plugins/core/ number-of-desktops 1
gsettings set org.compiz.core:/org/compiz/profiles/unity/plugins/core/ hsize 2
gsettings set org.compiz.core:/org/compiz/profiles/unity/plugins/core/ vsize 2