header #version 330 to
something lower like #version 120 in order to make @TheEmu 's supplement work.
Actually, I think the Opposite case.
ALL of the older shaders should have a Header updated to support version 330
unless the shader is using an obsolete / no longer functioning GLSL command.
All headers should be raised to the higher version.
330 as a minimum, 330 ( 2010 ) should support backward all prior versions.
moving in to the 4.0 version ( also 2010 ) , is where backward compatibility started to be lost.
460 is the current as of 2017.
ALL current GPU's should be supporting version 460 ( 4.6 )