diff --git a/lib/CPUs/MIPS/sim/tb_mips_muldiv.fdo b/lib/CPUs/MIPS/sim/tb_mips_muldiv.fdo
index efb8705..824cf1e 100644
--- a/lib/CPUs/MIPS/sim/tb_mips_muldiv.fdo
+++ b/lib/CPUs/MIPS/sim/tb_mips_muldiv.fdo
@@ -1,5 +1,7 @@
 ## NOTE:  Do not edit this file.
 ##
+if {[file exists work]} {vdel -lib work -all}
+
 vlib work
 vcom -explicit  -93 "../../../PCK_FIO-1.16/PCK_FIO.vhd"
 vcom -explicit  -93 "../src/core/mips_types.vhd"
diff --git a/lib/CPUs/MIPS/sim/tb_mips_sys.fdo b/lib/CPUs/MIPS/sim/tb_mips_sys.fdo
index bca6968..c6a5988 100644
--- a/lib/CPUs/MIPS/sim/tb_mips_sys.fdo
+++ b/lib/CPUs/MIPS/sim/tb_mips_sys.fdo
@@ -1,3 +1,5 @@
+if {[file exists work]} {vdel -lib work -all}
+
 vlib work
 vcom -explicit  -93 "../src/dpram_2w2r.vhd"
 vcom -explicit  -93 "../src/dpram_1w1r.vhd"