diff --git a/indra/newview/app_settings/shaders/class1/interface/downsampleDepthRectF.glsl b/indra/newview/app_settings/shaders/class1/interface/downsampleDepthRectF.glsl
index 2f89b8ed7211627e0216792dffab9e4b4322a406..0e5dc0818363afffa65038762f0ca726ce3d7069 100644
--- a/indra/newview/app_settings/shaders/class1/interface/downsampleDepthRectF.glsl
+++ b/indra/newview/app_settings/shaders/class1/interface/downsampleDepthRectF.glsl
@@ -23,6 +23,8 @@
  * $/LicenseInfo$
  */
 
+#extension GL_ARB_texture_rectangle : enable
+
 #ifdef DEFINE_GL_FRAGCOLOR
 out vec4 frag_color;
 #else