# Render to cubemap wrong Y values

I'm currently trying to render to a cubemap in order to blur it. However the top and bottom faces appear much closer than they should be in the blurred version. I thought the problem came from my transformation matrices but they're just rotations. I'm beginning to believe that it's the way I'm handling the framebuffer that's causing this problem. Here's how I'm doing it :

    unsigned fbo;
unsigned rt;
glViewport(0, 0, size, size);
glGenFramebuffers(1, &fbo);
glGenRenderbuffers(1, &rt);

glBindFramebuffer(GL_FRAMEBUFFER, fbo);
glBindRenderbuffer(GL_RENDERBUFFER, rt);
glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH_COMPONENT24, size, size);
glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, rt);

//...
//enable source cubemap, set projection
//...

for(int i = 0; i < 6; ++i) {
//set rotation
glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_CUBE_MAP_POSITIVE_X + i, target_cubemap, 0);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
//draw cube


(the images below are from the same corder)