diff --git a/lib/CPUs/MIPS/sim/tb_mips_top.fdo b/lib/CPUs/MIPS/sim/tb_mips_top.fdo
index 8df7836..05a3b4b 100644
--- a/lib/CPUs/MIPS/sim/tb_mips_top.fdo
+++ b/lib/CPUs/MIPS/sim/tb_mips_top.fdo
@@ -1,5 +1,8 @@
 ## NOTE:  Do not edit this file.
 ##
+
+if {[file exists work]} {vdel -lib work -all}
+
 vlib work
 
 # RAMS
diff --git a/lib/CPUs/MIPS/sim/tb_mips_top_syn.fdo b/lib/CPUs/MIPS/sim/tb_mips_top_syn.fdo
index d246ffa..b150fe1 100644
--- a/lib/CPUs/MIPS/sim/tb_mips_top_syn.fdo
+++ b/lib/CPUs/MIPS/sim/tb_mips_top_syn.fdo
@@ -1,5 +1,8 @@
 ## NOTE:  Do not edit this file.
 ##
+
+if {[file exists work]} {vdel -lib work -all}
+
 vlib work
 
 # UART