diff --git a/indra/newview/app_settings/shaders/class1/deferred/pbralphaF.glsl b/indra/newview/app_settings/shaders/class1/deferred/pbralphaF.glsl
index aec2a90bda17c79d347016734165d1335a531319..1caf2b2b1a7d4e2d816040d9978091ea8bfd3616 100644
--- a/indra/newview/app_settings/shaders/class1/deferred/pbralphaF.glsl
+++ b/indra/newview/app_settings/shaders/class1/deferred/pbralphaF.glsl
@@ -73,7 +73,7 @@ VARYING vec2 vary_texcoord1;
 VARYING vec2 vary_texcoord2;
 VARYING vec3 vary_normal;
 VARYING vec3 vary_tangent;
-VARYING float vary_sign;
+flat in float vary_sign;
 
 
 #ifdef HAS_ALPHA_MASK