diff --git a/modules/galaxy/shaders/billboard_fs.glsl b/modules/galaxy/shaders/billboard_fs.glsl
index 18fb39df76..cf758b3cab 100644
--- a/modules/galaxy/shaders/billboard_fs.glsl
+++ b/modules/galaxy/shaders/billboard_fs.glsl
@@ -29,8 +29,8 @@ uniform sampler2D psfTexture;
 
 in vec4 vs_position;
 in vec2 psfCoords;
-in vec3 ge_color;
-in float ge_screenSpaceDepth;
+flat in vec3 ge_color;
+flat in float ge_screenSpaceDepth;
 
 Fragment getFragment() {
     Fragment frag;