diff --git a/src/glsl/ir_variable.cpp b/src/glsl/ir_variable.cpp
index f357717..cff364e 100644
--- a/src/glsl/ir_variable.cpp
+++ b/src/glsl/ir_variable.cpp
@@ -38,6 +38,10 @@ static void
 generate_ARB_draw_instanced_variables(exec_list *,
                                       struct _mesa_glsl_parse_state *,
                                       bool, _mesa_glsl_parser_targets);
+                                      
+static void generate_EXT_gpu_shader4_variables(exec_list *,
+                                                  struct _mesa_glsl_parse_state *,
+                                                  bool, _mesa_glsl_parser_targets);
 
 static struct gl_builtin_uniform_element gl_DepthRange_elements[] = {
    {"near", {STATE_DEPTH_RANGE, 0, 0}, SWIZZLE_XXXX},
@@ -629,6 +633,8 @@ initialize_vs_variables(exec_list *instructions,
    if (state->ARB_draw_instanced_enable)
       generate_ARB_draw_instanced_variables(instructions, state, false,
                                             vertex_shader);
+   generate_EXT_gpu_shader4_variables(instructions, state, false, 
+                                              vertex_shader);
 }
 
 
@@ -749,6 +755,26 @@ generate_ARB_draw_instanced_variables(exec_list *instructions,
    }
 }
 
+static void
+generate_EXT_gpu_shader4_variables(exec_list *instructions,
+                                      struct _mesa_glsl_parse_state *state,
+                                      bool warn,
+                                      _mesa_glsl_parser_targets target)
+{
+   /* gl_InstanceID is only available in the vertex shader.
+    */
+   if (target == vertex_shader) {
+      if (state->ARB_draw_instanced_enable) {
+         add_variable(instructions, state->symbols,
+                       "gl_InstanceID", glsl_type::int_type,
+                       ir_var_system_value, SYSTEM_VALUE_INSTANCE_ID);
+      } else {
+         add_builtin_constant(instructions, state->symbols, 
+            "gl_InstanceID", 0);
+      }
+   }
+}
+
 
 static void
 generate_ARB_shader_stencil_export_variables(exec_list *instructions,