undefined variable "gl_position"

undefined variable "gl_position"

I'm trying to draw 2 simple triangles nothing special and this is the
shader code :
#version 430 core
layout(location=0) in vec4 vPosition;
void
main()
{
gl_position=vPosition;
}
As you can see the shader code is really small and has nothing special.
When I try to compile this code I get a
undefined variable "gl_position"
I don't understand why because I thought all the gl_... variables were
global variables.
What can I do ?