glslangValidator '-e' doesn't work correctly

[SC5Shout]

I've got this shader code:

#version 450

void mainVS() 
{
    gl_Position = vec4(0.0, 0.0, 0.0, 1.0);
}

and when I run

glslangValidator -V -S vert -e mainVS -o vertex_shader.spv shader.glsl

I get this error: ERROR: Linking vertex stage: Missing entry point: Each stage requires one entry point

when I change void mainVS() to void main() and run glslangValidator... again, it works fine.