diff --git a/src/compiler/glsl/glsl_to_nir.cpp b/src/compiler/glsl/glsl_to_nir.cpp
index 535c39dd27b..51712f3c058 100644
--- a/src/compiler/glsl/glsl_to_nir.cpp
+++ b/src/compiler/glsl/glsl_to_nir.cpp
@@ -561,6 +561,7 @@ nir_visitor::visit(ir_variable *ir)
    var->data.matrix_layout = ir->data.matrix_layout;
    var->data.from_named_ifc_block = ir->data.from_named_ifc_block;
    var->data.compact = false;
+   var->data.used = ir->data.used;
 
    switch(ir->data.mode) {
    case ir_var_auto:
diff --git a/src/compiler/nir/nir.h b/src/compiler/nir/nir.h
index 4eb67d95b82..e958bedc0cc 100644
--- a/src/compiler/nir/nir.h
+++ b/src/compiler/nir/nir.h
@@ -648,6 +648,15 @@ typedef struct nir_variable {
        */
       unsigned must_be_shader_input : 1;
 
+      /**
+       * Has this variable been used for reading or writing?
+       *
+       * Several GLSL semantic checks require knowledge of whether or not a
+       * variable has been used.  For example, it is an error to redeclare a
+       * variable as invariant after it has been used.
+       */
+      unsigned used:1;
+
       /**
        * How the variable was declared.  See nir_var_declaration_type.
        *