diff --git a/src/intel/compiler/brw_fs.cpp b/src/intel/compiler/brw_fs.cpp
index b8217b714ff..6a8bd0337d2 100644
--- a/src/intel/compiler/brw_fs.cpp
+++ b/src/intel/compiler/brw_fs.cpp
@@ -5826,6 +5826,7 @@ fs_visitor::lower_find_live_channel()
        */
       if (!(first && packed_dispatch)) {
          fs_reg mask = ubld.vgrf(BRW_REGISTER_TYPE_UD);
+         ubld.UNDEF(mask);
          ubld.emit(SHADER_OPCODE_READ_SR_REG, mask, brw_imm_ud(vmask ? 3 : 2));
 
          /* Quarter control has the effect of magically shifting the value of
@@ -5843,6 +5844,7 @@ fs_visitor::lower_find_live_channel()
          ubld.FBL(inst->dst, exec_mask);
       } else {
          fs_reg tmp = ubld.vgrf(BRW_REGISTER_TYPE_UD, 1);
+         ubld.UNDEF(tmp);
          ubld.LZD(tmp, exec_mask);
          ubld.ADD(inst->dst, negate(tmp), brw_imm_uw(31));
       }
diff --git a/src/intel/compiler/brw_lower_logical_sends.cpp b/src/intel/compiler/brw_lower_logical_sends.cpp
index d4cfa9dfacc..d86a9028aa4 100644
--- a/src/intel/compiler/brw_lower_logical_sends.cpp
+++ b/src/intel/compiler/brw_lower_logical_sends.cpp
@@ -1344,6 +1344,7 @@ emit_predicate_on_vector_mask(const fs_builder &bld, fs_inst *inst)
 
    const fs_visitor *v = static_cast<const fs_visitor *>(bld.shader);
    const fs_reg vector_mask = ubld.vgrf(BRW_REGISTER_TYPE_UW);
+   ubld.UNDEF(vector_mask);
    ubld.emit(SHADER_OPCODE_READ_SR_REG, vector_mask, brw_imm_ud(3));
    const unsigned subreg = sample_mask_flag_subreg(v);