diff --git a/.gitignore b/.gitignore
index 11f6ab8..8d37115 100644
--- a/.gitignore
+++ b/.gitignore
@@ -15,6 +15,7 @@ work
 transcript
 *.wlf
 *.vstf
+*.fst
 
 
 # pre-commit
diff --git a/devenv.nix b/devenv.nix
index 71c391f..9b45afd 100644
--- a/devenv.nix
+++ b/devenv.nix
@@ -42,7 +42,7 @@
     fi
 
     # Open the VCD file with GTKWave
-    gtkwave output.vcd
+    gtkwave --optimize output.vcd
   '';
 
   enterShell = ''