diff --git a/src/compiler/nir/nir_from_ssa.c b/src/compiler/nir/nir_from_ssa.c
index 3bcac93302c..7456eab7686 100644
--- a/src/compiler/nir/nir_from_ssa.c
+++ b/src/compiler/nir/nir_from_ssa.c
@@ -408,6 +408,9 @@ isolate_phi_nodes_block(nir_shader *shader, nir_block *block, void *dead_ctx)
       nir_phi_instr *phi = nir_instr_as_phi(instr);
       assert(phi->dest.is_ssa);
       nir_foreach_phi_src(src, phi) {
+         if (nir_src_is_undef(src->src))
+            continue;
+
          nir_parallel_copy_instr *pcopy =
             get_parallel_copy_at_end_of_block(src->pred);
          assert(pcopy);
@@ -460,6 +463,9 @@ coalesce_phi_nodes_block(nir_block *block, struct from_ssa_state *state)
 
       nir_foreach_phi_src(src, phi) {
          assert(src->src.is_ssa);
+         if (nir_src_is_undef(src->src))
+            continue;
+
          merge_node *src_node = get_merge_node(src->src.ssa, state);
          if (src_node->set != dest_node->set)
             merge_merge_sets(dest_node->set, src_node->set);