diff --git a/iverilog/run_testbench.bat b/iverilog/run_testbench.bat
index 8333245..42a9335 100644
--- a/iverilog/run_testbench.bat
+++ b/iverilog/run_testbench.bat
@@ -1,2 +1,2 @@
-iverilog -g2005 -s apple1_tb -o apple1_tb -c apple1_files.txt
+iverilog -DSIM -g2005 -s apple1_tb -o apple1_tb -c apple1_files.txt
 vvp apple1_tb