diff --git a/src/gallium/drivers/iris/iris_state.c b/src/gallium/drivers/iris/iris_state.c
index 4ef149f7060..e77f900a316 100644
--- a/src/gallium/drivers/iris/iris_state.c
+++ b/src/gallium/drivers/iris/iris_state.c
@@ -744,6 +744,7 @@ iris_emit_l3_config(struct iris_batch *batch,
                     const struct gen_l3_config *cfg)
 {
    uint32_t reg_val;
+   assert(cfg || GEN_GEN >= 12);
 
 #if GEN_GEN >= 12
 #define L3_ALLOCATION_REG GENX(L3ALLOC)
@@ -765,10 +766,16 @@ iris_emit_l3_config(struct iris_batch *batch,
       reg.ErrorDetectionBehaviorControl = true;
       reg.UseFullWays = true;
 #endif
-      reg.URBAllocation = cfg->n[GEN_L3P_URB];
-      reg.ROAllocation = cfg->n[GEN_L3P_RO];
-      reg.DCAllocation = cfg->n[GEN_L3P_DC];
-      reg.AllAllocation = cfg->n[GEN_L3P_ALL];
+      if (GEN_GEN < 12 || cfg) {
+         reg.URBAllocation = cfg->n[GEN_L3P_URB];
+         reg.ROAllocation = cfg->n[GEN_L3P_RO];
+         reg.DCAllocation = cfg->n[GEN_L3P_DC];
+         reg.AllAllocation = cfg->n[GEN_L3P_ALL];
+      } else {
+#if GEN_GEN >= 12
+         reg.L3FullWayAllocationEnable = true;
+#endif
+      }
    }
    _iris_emit_lri(batch, L3_ALLOCATION_REG_num, reg_val);
 }