diff --git a/src/intel/compiler/brw_nir_lower_cooperative_matrix.c b/src/intel/compiler/brw_nir_lower_cooperative_matrix.c
index 6d31342376b..8ed937baaed 100644
--- a/src/intel/compiler/brw_nir_lower_cooperative_matrix.c
+++ b/src/intel/compiler/brw_nir_lower_cooperative_matrix.c
@@ -678,7 +678,7 @@ lower_cmat_instr(nir_builder *b, nir_instr *instr, void *_state)
       nir_deref_instr *dst_slice = nir_src_as_deref(intrin->src[0]);
       nir_def *scalar = intrin->src[1].ssa;
       nir_deref_instr *src_slice = nir_src_as_deref(intrin->src[2]);
-      nir_def *dst_index = intrin->src[3].ssa;
+      const nir_src dst_index = intrin->src[3];
 
       const struct glsl_type *dst_mat_type = get_coop_type_for_slice(state, dst_slice);
       ASSERTED const struct glsl_type *src_mat_type = get_coop_type_for_slice(state, src_slice);
@@ -691,24 +691,34 @@ lower_cmat_instr(nir_builder *b, nir_instr *instr, void *_state)
       const unsigned packing_factor = get_packing_factor(desc, dst_slice->type);
       const unsigned num_components = glsl_get_vector_elements(dst_slice->type);
 
-      nir_def *slice_index = nir_udiv_imm(b, dst_index, packing_factor);
-      nir_def *vector_index = nir_umod_imm(b, dst_index, packing_factor);
+      nir_def *slice_index = nir_udiv_imm(b, dst_index.ssa, packing_factor);
+      nir_def *vector_index = nir_umod_imm(b, dst_index.ssa, packing_factor);
       nir_def *results[NIR_MAX_VEC_COMPONENTS];
 
+      const int slice_constant_index = nir_src_is_const(dst_index)
+         ? nir_src_as_uint(dst_index) / packing_factor
+         : -1;
+
       for (unsigned i = 0; i < num_components; i++) {
          nir_def *val = nir_channel(b, nir_load_deref(b, src_slice), i);
          nir_def *insert;
 
-         if (packing_factor == 1) {
-            insert = scalar;
-         } else {
-            nir_def *unpacked = nir_unpack_bits(b, val, bits);
-            nir_def *v = nir_vector_insert(b, unpacked, scalar, vector_index);
+         if (slice_constant_index < 0 || slice_constant_index == i) {
+            if (packing_factor == 1) {
+               insert = scalar;
+            } else {
+               nir_def *unpacked = nir_unpack_bits(b, val, bits);
+               nir_def *v = nir_vector_insert(b, unpacked, scalar, vector_index);
 
-            insert = nir_pack_bits(b, v, bits * packing_factor);
+               insert = nir_pack_bits(b, v, bits * packing_factor);
+            }
+         } else {
+            insert = val;
          }
 
-         results[i] = nir_bcsel(b, nir_ieq_imm(b, slice_index, i), insert, val);
+         results[i] = slice_constant_index < 0
+            ? nir_bcsel(b, nir_ieq_imm(b, slice_index, i), insert, val)
+            : insert;
       }
 
       nir_store_deref(b, dst_slice, nir_vec(b, results, num_components),