diff --git a/src/compiler/glsl/opt_dead_builtin_variables.cpp b/src/compiler/glsl/opt_dead_builtin_variables.cpp
index 48452fc312e..c03c243ac5d 100644
--- a/src/compiler/glsl/opt_dead_builtin_variables.cpp
+++ b/src/compiler/glsl/opt_dead_builtin_variables.cpp
@@ -36,8 +36,9 @@ void
 optimize_dead_builtin_variables(exec_list *instructions,
                                 enum ir_variable_mode other)
 {
-   foreach_in_list_safe(ir_variable, var, instructions) {
-      if (var->ir_type != ir_type_variable || var->data.used)
+   foreach_in_list_safe(ir_instruction, inst, instructions) {
+      ir_variable *var = inst->as_variable();
+      if (!var || var->data.used)
          continue;
 
       if (var->data.mode != ir_var_uniform