diff --git a/indra/newview/app_settings/shaders/class1/deferred/deferredUtil.glsl b/indra/newview/app_settings/shaders/class1/deferred/deferredUtil.glsl
index 1dd697b43d6fc4331722f18e518770c0003b6af3..dbcb995ba64afab0b99f75b8de878c365870cbcc 100644
--- a/indra/newview/app_settings/shaders/class1/deferred/deferredUtil.glsl
+++ b/indra/newview/app_settings/shaders/class1/deferred/deferredUtil.glsl
@@ -392,7 +392,7 @@ vec3 pbrIbl(vec3 diffuseColor,
             out vec3 specContrib)
 {
     // retrieve a scale and bias to F0. See [1], Figure 3
-    vec2 brdf = BRDF(clamp(nv, 0, 1), perceptualRough);
+    vec2 brdf = BRDF(clamp(nv, 0, 1), 1.0-perceptualRough);
     vec3 diffuseLight = irradiance;
     vec3 specularLight = radiance;