error C7621: #extension directive must occur before any non-preprocessor token

I get that error message from gstglslstage compiles this shader:

#version 300 es
 #ifdef GL_ES
 precision highp float;
 #endif
 #extension GL_OES_EGL_image_external_essl3 : require 
 uniform vec2 tex_scale0;
 uniform vec2 tex_scale1;
 uniform vec2 tex_scale2;
 uniform float width;
 uniform float height;
 uniform float poffset_x;
 uniform float poffset_y;
 uniform samplerExternalOES tex;
 
 layout (location = 0) out vec4 fragColor;
 
 in vec2 v_texcoord;
 void main (void) {
 vec2 texcoord;
 texcoord = v_texcoord;
 vec4 t = texture(tex, texcoord * tex_scale0);
 
 fragColor = vec4(t.r, t.g, t.b, t.a);
 
 }