diff --git a/src/riscv_instr_gen_config.sv b/src/riscv_instr_gen_config.sv
index 06818355..6e7dcbc2 100644
--- a/src/riscv_instr_gen_config.sv
+++ b/src/riscv_instr_gen_config.sv
@@ -274,10 +274,7 @@ class riscv_instr_gen_config extends uvm_object;
   int                    dist_control_mode;
   int unsigned           category_dist[riscv_instr_category_t];
 
-
   constraint default_c {
-    sub_program_instr_cnt.size() == num_of_sub_program;
-    debug_sub_program_instr_cnt.size() == num_debug_sub_program;
     main_program_instr_cnt inside {[10 : instr_cnt]};
     foreach(sub_program_instr_cnt[i]) {
       sub_program_instr_cnt[i] inside {[10 : instr_cnt]};
@@ -677,6 +674,9 @@ class riscv_instr_gen_config extends uvm_object;
   endfunction
 
   function void pre_randomize();
+    sub_program_instr_cnt = new[num_of_sub_program];
+    debug_sub_program_instr_cnt = new[num_debug_sub_program];
+
     foreach (riscv_instr_pkg::supported_privileged_mode[i]) begin
       if(riscv_instr_pkg::supported_privileged_mode[i] == SUPERVISOR_MODE)
         support_supervisor_mode = 1;