diff --git a/src/intel/compiler/brw_builder.h b/src/intel/compiler/brw_builder.h
index 9df8bd2138e..50ed09380d7 100644
--- a/src/intel/compiler/brw_builder.h
+++ b/src/intel/compiler/brw_builder.h
@@ -435,6 +435,17 @@ public:
       return inst;
    }
 
+   /**
+    * Emit UNDEF for the given register if its data doesn't fully occupy
+    * the space we allocated.
+    */
+   void
+   emit_undef_for_partial_reg(const brw_reg &reg) const
+   {
+      if (brw_type_size_bytes(reg.type) * dispatch_width() < REG_SIZE)
+         UNDEF(reg);
+   }
+
    /**
     * Assorted arithmetic ops.
     * @{
diff --git a/src/intel/compiler/brw_from_nir.cpp b/src/intel/compiler/brw_from_nir.cpp
index f45a9b78de7..57e64179c77 100644
--- a/src/intel/compiler/brw_from_nir.cpp
+++ b/src/intel/compiler/brw_from_nir.cpp
@@ -2034,8 +2034,7 @@ get_nir_def(nir_to_brw_state &ntb, const nir_def &def, bool all_sources_uniform)
 
       ntb.ssa_values[def.index].is_scalar = is_scalar;
 
-      if (def.bit_size * bld.dispatch_width() < 8 * REG_SIZE)
-         bld.UNDEF(ntb.ssa_values[def.index]);
+      bld.emit_undef_for_partial_reg(ntb.ssa_values[def.index]);
 
       return ntb.ssa_values[def.index];
    } else {