diff --git a/extra/terrain/shaders/shaders.factor b/extra/terrain/shaders/shaders.factor
index 630163c724..9233ab3f36 100644
--- a/extra/terrain/shaders/shaders.factor
+++ b/extra/terrain/shaders/shaders.factor
@@ -12,6 +12,7 @@ void main()
     gl_Position = v;
 
     vec4 p = gl_ProjectionMatrixInverse * v;
+    p.z = -abs(p.z);
     
     float s = sin(sky_theta), c = cos(sky_theta);
     direction = mat3(1, 0, 0,  0, c, s,  0, -s, c)