https://bugzilla.redhat.com/show_bug.cgi?id=1134299
--- Comment #2 from Mike FABIAN mfabian@redhat.com --- I can also reproduce this on f20.
$ gsettings get org.gnome.desktop.input-sources xkb-options ['terminate:ctrl_alt_bksp', '', 'eurosign:5', 'grp:rctrl_rshift_toggle']
I have Super+Space set as the switch to next input source and (just as the reporter) RightCtrl+RightShift as the modifier only input source switch.
I can now use *all* of the following key combinations to switch input sources:
RightCtrl+RightShift LeftCtrl+RightShift LeftAlt+RightShift LeftShift+RightShift