diff --git a/src/intel/compiler/brw_fs_nir.cpp b/src/intel/compiler/brw_fs_nir.cpp
index dd7205b506a..f13adf5c5d4 100644
--- a/src/intel/compiler/brw_fs_nir.cpp
+++ b/src/intel/compiler/brw_fs_nir.cpp
@@ -282,6 +282,7 @@ fs_visitor::nir_emit_system_values()
       const fs_builder abld = bld.annotate("gl_SubgroupInvocation", NULL);
       fs_reg &reg = nir_system_values[SYSTEM_VALUE_SUBGROUP_INVOCATION];
       reg = abld.vgrf(BRW_REGISTER_TYPE_UW);
+      abld.UNDEF(reg);
 
       const fs_builder allbld8 = abld.group(8, 0).exec_all();
       allbld8.MOV(reg, brw_imm_v(0x76543210));