diff --git a/src/compiler/nir/nir.h b/src/compiler/nir/nir.h
index 5e06f163b81..c6b788e28b7 100644
--- a/src/compiler/nir/nir.h
+++ b/src/compiler/nir/nir.h
@@ -5408,6 +5408,7 @@ typedef struct nir_lower_compute_system_values_options {
    bool lower_local_invocation_index:1;
    bool lower_cs_local_id_to_index:1;
    bool lower_workgroup_id_to_index:1;
+   uint16_t num_workgroups[3]; /* Compile-time-known dispatch sizes, or 0 if unknown. */
 } nir_lower_compute_system_values_options;
 
 bool nir_lower_compute_system_values(nir_shader *shader,
diff --git a/src/compiler/nir/nir_lower_system_values.c b/src/compiler/nir/nir_lower_system_values.c
index 5253efd0098..9904cc80543 100644
--- a/src/compiler/nir/nir_lower_system_values.c
+++ b/src/compiler/nir/nir_lower_system_values.c
@@ -672,10 +672,18 @@ lower_compute_system_value_instr(nir_builder *b,
       if (options && options->has_base_workgroup_id)
          return nir_iadd(b, nir_u2uN(b, nir_load_workgroup_id_zero_base(b), bit_size),
                             nir_load_base_workgroup_id(b, bit_size));
-      else if (options && options->lower_workgroup_id_to_index)
-         return lower_id_to_index_no_umod(b, nir_load_workgroup_index(b),
+      else if (options && options->lower_workgroup_id_to_index) {
+         nir_ssa_def *wg_idx = nir_load_workgroup_index(b);
+
+         nir_ssa_def *val =
+               try_lower_id_to_index_1d(b, wg_idx, options->num_workgroups);
+         if (val)
+            return val;
+
+         return lower_id_to_index_no_umod(b, wg_idx,
                                           nir_load_num_workgroups(b, bit_size),
                                           bit_size);
+      }
 
       return NULL;