diff --git a/Makefile b/Makefile
index 1dee0922d8e504b4f45e4bed3745123550001dba..71a42562b3f2a922f1924d3049d0fa10591399ed 100644
--- a/Makefile
+++ b/Makefile
@@ -40,3 +40,5 @@ clean:
 	rm -rf /tmp/go.*.mod
 	rm -rf /tmp/go.*.sum
 	rm -rf ./examples/*.csv
+	rm -rf ./ackley/*delme*
+	rm -rf ./ackley/*jpg
diff --git a/ackley/ackley_test.go b/ackley/ackley_test.go
index 77bf85bad2208aa193dea3a0cc2e7bb031ad673c..0795420468ffe4d274bd5860c1be92db2225c215 100644
--- a/ackley/ackley_test.go
+++ b/ackley/ackley_test.go
@@ -65,7 +65,7 @@ func TestAckley1d(t *testing.T) {
 	set term "jpeg"
 	set output "test1d.jpg"
 
-	plot 'test1d.dat' us 2:1 with line`
+	plot 'test1d_delme.dat' us 2:1 with line`
 	const fOutName = "test1d_delme.dat"
 	const plotNoteName = "plot1d_delme.gplt"
 	grid := grdsz{-10, 10, 500}
@@ -99,7 +99,7 @@ func TestAckley2d(t *testing.T) {
 	set term "jpeg"
 	set output "test2d.jpg"
 
-	splot 'test2d.dat' us 2:3:1 with points`
+	splot 'test2d_delme.dat' us 2:3:1 with points`
 	const fOutName = "test2d_delme.dat"
 	const plotNoteName = "plot2d_delme.gplt"
 	grid := grdsz{-5, 5, 40}