diff --git a/test-iverilog/__build.sh b/test-iverilog/__build.sh
index 5c1c2ac..ebcc374 100755
--- a/test-iverilog/__build.sh
+++ b/test-iverilog/__build.sh
@@ -1,3 +1,5 @@
 #!/usr/bin/env bash
 
-iverilog -g2012 -o top -f ../source/sources.f top.sv
+FFILE=../source/sources.f
+
+iverilog -g2012 -o top -f $FFILE top.sv
diff --git a/test-modelsim/__build.sh b/test-modelsim/__build.sh
index b21b91e..6531e18 100755
--- a/test-modelsim/__build.sh
+++ b/test-modelsim/__build.sh
@@ -1,5 +1,7 @@
 #!/usr/bin/env bash
 set -e
 
+FFILE=../source/sources.f
+
 rm -rf testbench
-vlog -sv -work testbench -vopt -f ../source/sources.f top.sv
+vlog -sv -work testbench -vopt -f $FFILE top.sv